feat(android): the phone's "More" is a bottom sheet

The tab bar's fifth item opened `<app-sidebar>` in a `wa-drawer`
sliding in from the side, which is a desktop shape put on a phone: a
200px column of a 424px screen, opening away from the thumb that asked
for it, with the rest of its 400px band empty. It also had three nested
scrollers in it -- the dialog, its body, and the sidebar's own
`overflow-y: auto` host -- so which box a drag moved depended on where
the finger landed, which is the "only part of the screen scrolls under
my finger" in the report.

It is the same element with `placement="bottom"` and `without-header`,
so the surface is the sheet #60 already built rather than a second
pattern: a `wa-drawer` is a native `<dialog>` opened with `showModal()`,
which is exactly the top layer that finding rests on, so the focus
trap, Escape, tap-outside and `wa-after-hide` come along unchanged and
nothing new has to be proved about paint containment.

The sidebar is still mounted rather than re-listed as data, because the
shell's own copy is `display: none` below 600px rather than removed --
a second list drawing `nav-*` handles is the duplicate-testid failure
this component already renders conditionally to avoid. What `expanded`
means had to grow to say the host owns the *box*: `app-sidebar` writes
an inline width and caps itself at 400px, which beats any rule the host
could write, so the width, the scrolling and the mouse-only resize
handle now follow that attribute. The rows are 48px below 600px, stated
in the sidebar's own stylesheet since that is the only place it renders
there.

Measured in the running app at 424x439: the sheet is 424 wide, 373 tall
(85vh, so there is an outside to tap), rows 48px, one scroller with
`overscroll-behavior: contain`, and Settings' row reachable at the end
of it. Desktop and Compact are untouched.

Closes #71

frontend/src/components/bottom-nav/bottom-nav.ts

@@ -27,15 +27,43 @@ interface Tab {
  * three to five items before the targets stop being thumb-sized —
  * 360 px over eleven sidebar entries is 32 px each — so the four here
  * are the ones plan 016's subset says a phone is *for*, and "More"
- * opens the existing `<app-sidebar>` in a drawer. That is deliberately
+ * opens the existing `<app-sidebar>` in a sheet. That is deliberately
  * a reuse rather than a second nav: two lists of destinations is two
  * places to add the next view to, and the sidebar already carries the
  * drag-to-navigate behaviour, the active state and the labels.
  *
+ * **"More" rises from the bottom, and it is the same sheet a context
+ * menu is** (#71). It was a `wa-drawer` sliding in from the side: a
+ * 200px column of a 424px screen, opening away from the thumb that
+ * asked for it, with three nested scrollers in it — the dialog, its
+ * body, and the sidebar's own `overflow-y: auto` host — which is the
+ * "only part of the screen scrolls under my finger" in the report.
+ *
+ * Three things about the replacement are load-bearing.
+ *
+ * **It is the same element with another `placement`, not a new
+ * surface.** `wa-drawer` renders a native `<dialog>` and opens it with
+ * `showModal()`, which is exactly what `menu-surface`'s sheet relies
+ * on — Chrome 37, the real top layer — so #60's containment finding
+ * carries over with nothing new to prove, and the focus trap, Escape,
+ * tap-outside and `wa-after-hide` all come along unchanged.
+ *
+ * **The body is the only scroller**, with `overscroll-behavior:
+ * contain`, and the sidebar is told to stop being one. Nesting them is
+ * what makes a drag scroll the wrong box.
+ *
+ * **The sidebar is still mounted rather than re-listed as data**,
+ * which the issue offers as an alternative. Its `data-testid` per
+ * destination is the reason: the shell's own sidebar is `display:
+ * none` below 600px rather than removed, so a second list drawing
+ * `nav-*` handles is the duplication this component already renders
+ * conditionally to avoid — and it would be a second place to add the
+ * next view to, with its own copy of #25's visibility filter.
+ *
  * It emits the same bubbling, composed `navigate` event the sidebar
  * does, so `index.ts` needs no knowledge of it, and it listens for that
  * event globally for the same reason the sidebar does: a navigation it
- * did not send (a card click, a detail view, the drawer) still has to
+ * did not send (a card click, a detail view, the sheet) still has to
  * move the highlight.
  */
 @customElement('bottom-nav')
@@ -115,15 +143,50 @@ export class BottomNav extends LitElement {
             white-space: nowrap;
         }
 
-        wa-drawer::part(body) {
-            padding: 0;
+        /* The sheet. --size is the drawer's own API for the axis its
+           placement uses, so auto is what makes it hug its content
+           instead of being a fixed 25rem band; the rest is the shape
+           the menu-surface context sheet already has, so a phone meets
+           one sheet rather than two. 85vh for its reason too: a surface
+           covering the whole screen is a page, not a sheet. */
+        wa-drawer {
+            --size: auto;
         }
 
-        app-sidebar {
-            /* The sidebar sizes itself inline and collapses to icons
-               below 900px, which is every phone.  In the drawer there
-               is room for the labels, so it is told not to. */
-            height: 100%;
+        wa-drawer::part(dialog) {
+            max-height: 85vh;
+            border-radius: 12px 12px 0 0;
+            /* The sidebar paints its own surface, so the sheet takes
+               that colour rather than the menus' elevated one: two
+               greys in one sheet is a seam across the middle of it. */
+            background-color: var(--yj-bg-surface, #212529);
+            /* One scroller, and it is the body below. The dialog's own
+               overflow: auto is what let the sheet scroll as well as
+               its content, and it is also what would square off the
+               corners this rule just rounded. */
+            overflow: hidden;
+        }
+
+        wa-drawer::part(body) {
+            padding: 0;
+            /* A scroll that reaches the end of this list must not
+               become a scroll of the page underneath it. */
+            overscroll-behavior: contain;
+            /* The sheet sits on the bottom edge, so the last
+               destination would otherwise be under the home indicator
+               on a gesture-navigation phone -- the same allowance the
+               bar itself makes above. */
+            padding-bottom: env(safe-area-inset-bottom, 0);
+        }
+
+        /* A sheet is dragged at with a thumb, so it says where its top
+           edge is. Decorative: the destinations are below it. */
+        .grip {
+            width: 36px;
+            height: 4px;
+            margin: 8px auto 4px;
+            border-radius: 2px;
+            background: var(--yj-text-tertiary, #888);
         }
     `];
 
@@ -158,7 +221,7 @@ export class BottomNav extends LitElement {
     private visibilityCtrl = new ViewVisibilityController(this);
 
     /**
-     * Whether the drawer has been asked for.
+     * Whether the sheet has been asked for.
      *
      * The sidebar inside it is rendered only while this is true, and
      * that is not an optimisation. `app-sidebar` carries a
@@ -200,15 +263,17 @@ export class BottomNav extends LitElement {
 
     override updated() {
         // Web Awesome renders its heading into its own shadow root and
-        // never points aria-labelledby at it, so the drawer would
+        // never points aria-labelledby at it, so the sheet would
         // otherwise be announced unnamed -- the same fix, and the same
         // reason, as every wa-dialog in the app. A drawer's shadow root
-        // has the same shape, so the helper needs no change.
+        // has the same shape, so the helper needs no change; under
+        // `without-header` there is no heading to point at, which is
+        // that helper's documented `aria-label` path.
         nameDialog(this.drawer);
     }
 
     private onGlobalNavigate = () => {
-        // A navigation from inside the drawer is the drawer's job done.
+        // A navigation from inside the sheet is the sheet's job done.
         // The highlight is not this listener's business any more.
         this.drawerOpen = false;
     };
@@ -274,12 +339,14 @@ export class BottomNav extends LitElement {
             </nav>
 
             <wa-drawer
-                placement="start"
+                placement="bottom"
+                without-header
                 label="All views"
                 data-testid="nav-drawer"
                 ?open=${this.drawerOpen}
                 @wa-after-hide=${this.onDrawerHide}
             >
+                <div class="grip"></div>
                 ${this.drawerOpen
                     ? html`<app-sidebar expanded></app-sidebar>`
                     : nothing}

frontend/src/components/sidebar/app-sidebar.ts

@@ -42,6 +42,26 @@ export class AppSidebar extends LitElement {
             scrollbar-width: thin;
         }
 
+        /* A host that has made room owns the box, not just the labels
+           (#71). The bottom-nav sheet is the width of the screen and
+           provides the one scroll container it needs; left to itself
+           the sidebar is a 200px column with a second scroller inside
+           it, which is what a nested scroll region feels like under a
+           thumb -- part of the surface moves and part of it does not. */
+        :host([expanded]) {
+            max-width: none;
+            height: auto;
+            overflow: visible;
+        }
+
+        /* And the width is not draggable there. It is a mouse
+           affordance (mousedown, col-resize) sitting on the right edge
+           of a touch surface, where the compatibility mouse events a
+           tap synthesises can start a resize nobody asked for. */
+        :host([expanded]) .resize-handle {
+            display: none;
+        }
+
         .resize-handle {
             position: absolute;
             top: 0;
@@ -160,6 +180,25 @@ export class AppSidebar extends LitElement {
         :host(.collapsed) li button wa-icon {
             font-size: var(--yj-icon-md);
         }
+
+        /* Below 600px the only place this renders is the bottom-nav
+           sheet -- the shell's own copy is display: none there -- so
+           the rows are sized for the thumb that opened it: 48px, which
+           is #186's floor and the height every row in #60's context
+           sheet already has. A media query inside a shadow root is
+           answered by the viewport, so the component states this
+           itself rather than the sheet reaching in. */
+        @media (max-width: 599px) {
+            ul {
+                padding: 4px 8px 8px;
+            }
+
+            li button {
+                min-height: 48px;
+                padding: 12px 10px;
+                gap: 14px;
+            }
+        }
     `];
 
     /** Delay in ms before a drag-hover triggers navigation. */
@@ -188,11 +227,14 @@ export class AppSidebar extends LitElement {
 
     /**
      * Keep the labels regardless of the viewport, for a host that has
-     * made room for them -- `bottom-nav`'s drawer, which is the whole
+     * made room for them -- `bottom-nav`'s sheet, which is the whole
      * screen wide on the phone where this would otherwise auto-collapse
      * to icons. The auto-collapse is a *width* response to a narrow
-     * shell, and inside a drawer the shell is not what the sidebar is
+     * shell, and inside a sheet the shell is not what the sidebar is
      * sharing space with.
+     *
+     * It says the host owns the *box*, not only the labels: the width,
+     * the scrolling and the resize handle all follow it (#71).
      */
     @property({ type: Boolean, reflect: true })
     expanded = false;
@@ -365,9 +407,18 @@ export class AppSidebar extends LitElement {
      * be a media query in the stylesheet.
      */
     private applyViewportWidth() {
-        const narrow =
-            !this.expanded &&
-            (this.narrowViewport?.matches ?? false);
+        // A host that made room decides how much: `bottom-nav`'s sheet
+        // is the whole screen wide, and the inline width below -- which
+        // beats any rule the host could write -- would draw the old
+        // 200px side drawer inside it.
+        if (this.expanded) {
+            this.style.width = '100%';
+            this.collapsed = false;
+
+            return;
+        }
+
+        const narrow = this.narrowViewport?.matches ?? false;
         const width = narrow
             ? MIN_WIDTH
             : this.userWidth;