test(ui): refresh two stale baselines and settle whether they gate

`make ui-visual` had been red on main since #27, and nothing runs it,
so four references had drifted across three unrelated merges. Two were
refreshed with #186; these are the other two.

Each recorded two changes, not one. `app-sidebar` lost Jobs (#27,
shipped) and moved its highlight from Home to Tracks; `now-playing`
gained the source line (shipped) and was playing from "a dynamic mix".
Both are singleton stores read by a case that sets nothing, so the shot
photographs whatever the case above it left behind — blessing that
would have pinned the file's own ordering into a PNG. Both cases state
their world now, and only then are the references re-recorded.

The second half of the issue asks whether this tier should gate, and
the answer is measured rather than preferred: replayed in a bare
ubuntu:24.04 container — CI's `check` image — three of the ten
baselines fail on rendering alone (`track-info` and one `page-header`
shot at ratio 0.03 against a 0.02 allowance, `seek-bar` one pixel
shorter), and the two stale ones disagree about their new height
between the machines. So CI cannot run this suite without a second,
container-recorded baseline set that every local run would then fail
against, and a pre-push hook is the same fault with the machines
swapped. It stays local and opt-in; what replaces the gate is the rule
that a change moving a component's geometry refreshes that component's
baseline in the same commit, having read the image, and never one it
did not cause. Written where a person meets it: the skill's tier doc
has the table, SKILL.md has the obligation, CLAUDE.md has the
constraint.

Deleting the baselines was the third option and is declined: this tier
has caught one thing no other could, the `<span>` that lost the UA
stylesheet's `box-sizing` and grew a badge 36→38px.

Closes #196

frontend/test/components/chrome.test.ts

@@ -137,6 +137,11 @@ describe('<app-sidebar>', () => {
   });
 
   it('looks the way it did last time', async () => {
+    // Stated rather than inherited: `activeViewStore` is a singleton, so
+    // without this the shot records whichever view the *previous* case
+    // left in it and the reference moves when the file is reordered.
+    activeViewStore.setView('home', true);
+
     const el = await fixture('app-sidebar');
 
     await visual(el, 'app-sidebar');