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/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;