feat(harness): agent-drivable dev harness and CI that gates

A coding agent could develop this repo's Go packages and could not
develop the application: every path to running YellowJacket ended in a
blocking GTK window, so 265 bound methods, 46 events, 33 component
directories and 13 stores had exactly one form of verification
available — `tsc --noEmit`.

The unlock is that `wails dev`'s dev server on :34115 serves the real
frontend with the real generated bindings against the same Go backend a
desktop window attaches to, so a plain Chromium under Xvfb gets a fully
functional app. Four test tiers now exist, cheapest first:

- `make ui-test` — 313 Vitest tests in a real browser in ~2 s, no app,
  no backend, no display. Works because `frontend/wailsjs/` is a pure
  passthrough to `window.go`/`window.runtime`, so faking just those two
  globals runs the real bindings and the real store code.
- `make test` — services in-process, asserting on the payload the
  frontend would receive, via a new `events.Emit` wrapper.
- `make dev-headless` + `playwright-cli` — the real app, driven
  interactively, with an event bridge on `window.__yjEvents` and a
  dev-only control surface at `/__test/`.
- `make e2e` — 19 of those flows frozen as Playwright specs.

`events.Emit(ctx, …)` replaces all 35 direct `runtime.EventsEmit` call
sites: wails' `getEvents` `log.Fatalf`s on any context without its
runtime, so those paths could not run under test and a background
worker could take the app down. Four packages had each hand-rolled the
same guard; nine more guarded on `ctx != nil`, which does not help.
`TestNoDirectRuntimeEmits` fails the build on a new one.

Fixtures are generated, not committed (`make testdata`), and seeds are
built by *running the app* — never by hand-writing config and DB rows,
which would be a second description of a valid YJ_HOME.

`.gitea/workflows/ci.yml` is the first workflow here that tests
anything; the other three only package, so `gitea_ci` reported only
packaging jobs and misled anyone asking whether a push was healthy.
Both jobs were prototyped to green in a bare ubuntu:24.04 container
before the YAML was written, which immediately caught `make lint`
linting three configurations that nothing builds: all three passes
omitted `webkit2_41`, so wails resolved webkit2gtk-4.0 — which Arch
still ships and Ubuntu 24.04 dropped.

Operational instructions live in `.pi/skills/yellowjacket-dev/`,
measured discoveries in `.planning/NOTES.md`, and architecture in
`CLAUDE.md` — split by tense, not by topic, because a topical split
gives every new fact two plausible homes. `make skill-check` fails a
commit if the skill cites a make target that does not exist.

frontend/test/stores/view-stores.test.ts

@@ -0,0 +1,189 @@
+/**
+ * The three small stores behind view chrome: the global search term,
+ * the track list's column set, and the explore cache that keeps detail
+ * pages from re-fetching what a search already returned.
+ */
+import { describe, expect, it, beforeEach } from 'vitest';
+
+import { searchStore } from '@store/search-store';
+import { trackListStore } from '@store/tracklist-store';
+import { exploreCache } from '@store/explore-cache';
+import { Events } from '../../src/events';
+import { emit, lastCall, flush } from '@test/support/harness';
+
+describe('search store', () => {
+  beforeEach(() => {
+    searchStore.setTerm('');
+    searchStore.setCurrentView('tracks');
+  });
+
+  it('holds the term', () => {
+    searchStore.setTerm('bowie');
+
+    expect(searchStore.getTerm()).toBe('bowie');
+  });
+
+  it('does not notify when the term is unchanged', () => {
+    let notifications = 0;
+    const off = searchStore.subscribe(() => {
+      notifications += 1;
+    });
+
+    searchStore.setTerm('bowie');
+    searchStore.setTerm('bowie');
+    off();
+
+    expect(notifications).toBe(1);
+  });
+
+  it('notifies synchronously — the search box has no batching to hide behind', () => {
+    let notified = false;
+    const off = searchStore.subscribe(() => {
+      notified = true;
+    });
+
+    searchStore.setTerm('x');
+    off();
+
+    expect(notified).toBe(true);
+  });
+
+  it('knows which views the search box applies to', () => {
+    const searchable = [
+      'tracks',
+      'albums',
+      'playlists',
+      'playlist-details',
+      'artists',
+      'genres',
+    ].map((view) => {
+      searchStore.setCurrentView(view);
+
+      return searchStore.isSearchableView();
+    });
+
+    expect(searchable.every(Boolean)).toBe(true);
+  });
+
+  it('hides the search box on views it cannot filter', () => {
+    const results = ['settings', 'explore', 'jobs', 'downloads'].map((view) => {
+      searchStore.setCurrentView(view);
+
+      return searchStore.isSearchableView();
+    });
+
+    expect(results).toEqual([false, false, false, false]);
+  });
+});
+
+describe('track list store', () => {
+  it('starts from the default column set', () => {
+    expect(trackListStore.getState().columnIds.length).toBeGreaterThan(0);
+  });
+
+  it('adopts the column order the backend pushes', () => {
+    emit(Events.TrackListConfigChanged, {
+      columns: [{ id: 'title' }, { id: 'artist' }],
+    });
+
+    expect(trackListStore.getState().columnIds).toEqual(['title', 'artist']);
+  });
+
+  it('sends columns back as objects, the shape the Go binding expects', async () => {
+    await trackListStore.setColumns(['title', 'album']);
+
+    // A bare string array would be a type mismatch, and a Wails binding
+    // called with wrong argument types never settles its callback.
+    expect(lastCall('config.Config.SetTrackListColumns')?.args).toEqual([
+      [{ id: 'title' }, { id: 'album' }],
+    ]);
+  });
+
+  it('does not apply a column change until the backend confirms it', async () => {
+    emit(Events.TrackListConfigChanged, { columns: [{ id: 'title' }] });
+    await trackListStore.setColumns(['title', 'album', 'year']);
+    await flush();
+
+    expect(trackListStore.getState().columnIds).toEqual(['title']);
+  });
+});
+
+describe('explore cache', () => {
+  it('round-trips an artist by mbid', () => {
+    exploreCache.setArtist('mbid-1', { mbid: 'mbid-1', name: 'Bowie' });
+
+    expect(exploreCache.getArtist('mbid-1')?.name).toBe('Bowie');
+  });
+
+  it('misses cleanly for an unknown mbid', () => {
+    expect(exploreCache.getArtist('nothing-here')).toBeUndefined();
+  });
+
+  it('refuses to key anything under an empty mbid', () => {
+    // An empty key would collide across every unidentified entity.
+    exploreCache.setArtist('', { mbid: '', name: 'Unknown' });
+    exploreCache.setAlbum('', { mbid: '', title: 'X', artistName: 'Y' });
+
+    expect([exploreCache.getArtist(''), exploreCache.getAlbum('')]).toEqual([
+      undefined,
+      undefined,
+    ]);
+  });
+
+  it('overwrites an entry with richer data from a later fetch', () => {
+    exploreCache.setArtist('mbid-2', { mbid: 'mbid-2', name: 'Eno' });
+    exploreCache.setArtist('mbid-2', {
+      mbid: 'mbid-2',
+      name: 'Eno',
+      imageURL: 'http://x/eno.jpg',
+    });
+
+    expect(exploreCache.getArtist('mbid-2')?.imageURL).toBe('http://x/eno.jpg');
+  });
+
+  it('caches an artist’s release groups and top tracks separately', () => {
+    exploreCache.setArtistAlbums('mbid-3', [{ mbid: 'rg-1' }] as never);
+    exploreCache.setArtistTopTracks('mbid-3', [{ mbid: 'rec-1' }] as never);
+
+    expect([
+      exploreCache.getArtistAlbums('mbid-3')?.length,
+      exploreCache.getArtistTopTracks('mbid-3')?.length,
+    ]).toEqual([1, 1]);
+  });
+
+  it('populates artists and albums from one search result', () => {
+    exploreCache.populateFromSearch(
+      [{ mbid: 'a-1', name: 'Artist', _imageSmall: 's.jpg' }],
+      [
+        {
+          mbid: 'rg-1',
+          title: 'Album',
+          artistCredit: 'Artist',
+          _coverArt: 'c.jpg',
+          firstReleaseDate: '1977',
+        },
+      ],
+    );
+
+    expect([
+      exploreCache.getArtist('a-1')?.imageSmall,
+      exploreCache.getAlbum('rg-1')?.year,
+      exploreCache.getAlbum('rg-1')?.artistName,
+    ]).toEqual(['s.jpg', '1977', 'Artist']);
+  });
+
+  it('defaults a missing artist credit to empty rather than undefined', () => {
+    exploreCache.populateFromSearch([], [{ mbid: 'rg-2', title: 'Untitled' }]);
+
+    expect(exploreCache.getAlbum('rg-2')?.artistName).toBe('');
+  });
+
+  it('skips search entries that carry no mbid', () => {
+    exploreCache.populateFromSearch(
+      [{ name: 'Nameless' }],
+      [{ title: 'Nameless' }],
+    );
+
+    expect(exploreCache.getArtist('')).toBeUndefined();
+  });
+});