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.

.pi/journal.md

@@ -0,0 +1,112 @@
+# Work log
+
+Temporal memory: what happened and what's next. Structure lives in
+`CLAUDE.md`, operational instructions in `.pi/skills/yellowjacket-dev/`,
+measured discoveries in `.planning/NOTES.md`. Don't duplicate those here.
+
+## Current state
+
+Plan 005 (agent development harness) is **complete — all seven
+phases**. Everything from phase 1 onward is still **uncommitted**: one
+large but coherent working-tree diff, nothing pushed.
+
+All four tiers verified green from a cold, cleaned state:
+`make ui-test` 313 passed, `make lint` 0 issues × 3 configurations,
+`make test` green × 3 passes, `make e2e` 19 passed. Both CI jobs
+verified green in a bare `ubuntu:24.04` container, including 19/19 on
+WebKit.
+
+- [ ] **Push `.gitea/workflows/ci.yml` and confirm with `gitea_ci`.**
+      Nothing has run on the shared runner yet — the whole workflow was
+      validated locally in Docker. A run that never starts looks
+      identical to one that passed, so the push is not done until
+      `gitea_ci` says so.
+- [ ] Decide whether to commit phases 1–7 as one commit or split by
+      phase (waiting on the user; nothing is committed yet).
+
+Unverified on the real runner, and the likeliest first failures:
+`actions/upload-artifact` needs node in the container (it is installed
+by an earlier step, and the step is `continue-on-error`, so a failure
+there cannot mask a real one); and the `npm_config_store_dir` pnpm
+cache is best-effort — if pnpm ignores it we lose warmth, nothing else.
+
+Open items deliberately not fixed: WAV tags are write-only
+(`TestWAVTagsAreNotReadableYet`), `themeStore.loadFromBackend`'s failure
+handler cannot recover, `backend/playlist` has no CRUD suite.
+
+## Log
+
+### 2026-08-11 — cold skill run, then phase 7 (CI)
+
+- **Followed the skill cold first**, as the last session asked. It
+  works: app up from a wiped `.dev/`, an undocumented flow driven
+  (queue panel + shuffle, asserted on `QueueModeChanged`), stopped —
+  ~1 minute, no dead ends. One real config bug: `outputDir` in
+  `.playwright/cli.config.json` resolves against **cwd**, not the
+  config file's directory (only `initScript` does that), so snapshots
+  were landing above the repo and a *stale* one from the previous
+  session answered `ls -t` instead. That cost a DOM walk to disprove a
+  regression that did not exist. Four smaller doc gaps fixed
+  (`sandbox-seed` already runs `testdata`; `ui-setup`/`e2e-setup` were
+  undocumented prerequisites; `snapshot` prints a path; `dev-stop`
+  leaves the browser open), plus `dev-headless.sh`'s own banner, which
+  was suggesting the bare `window.go` call its next paragraph warns
+  against.
+- **Built both CI jobs as container scripts before writing any YAML**,
+  then transcribed the YAML back out and re-ran it to prove the
+  transcription. Push-and-see is a bad loop on a self-hosted runner.
+- **It found a real bug immediately**: `make lint` omitted
+  `webkit2_41` on all three passes, so it was linting configurations
+  nothing builds. Invisible on Arch (which still ships
+  `webkit2gtk-4.0.pc`), fatal on Ubuntu 24.04. Tag sets now match
+  `make test`.
+- **Both open decisions settled by measurement**: ALSA `null` PCM for
+  audio (no daemon; the elapsed clock really advances), dead-address
+  stub for the explore artifact (and setting it for the *app* run, not
+  just seeding, is worth 8x on suite wall clock). **WebKit is a
+  required step** — it had never been run anywhere, so one throwaway
+  container run replaced a coin flip with 19/19 at +11 s.
+
+### 2026-08-10 — phase 6, pi affordances
+
+- Added `.pi/skills/yellowjacket-dev/` as a directory rather than a flat
+  file: only the description is always in context, so `SKILL.md` stays
+  short enough that reading it whole is never a decision, and the deeper
+  material sits in `references/{harness,fixtures,ui-tier,schema-change}.md`.
+- Settled the CLAUDE.md-vs-skill split **grammatically, not topically**,
+  because a topical split is what rots — every new fact gets two
+  plausible homes. Three docs, three tenses: NOTES.md is past
+  (measured, dated, append-only), CLAUDE.md is present (what the system
+  is), the skill is imperative (what to run). A new paragraph's tense
+  decides where it goes.
+- The five gotchas (binding timeouts, first-run wizard, `pkill -f`,
+  seeds-by-running, WebKit-is-CI-only) went **inline in SKILL.md**, not
+  into a reference: you need them before the failure, not after.
+- Trimmed CLAUDE.md's "Fixtures and the headless harness" section by
+  about half — the command sequences and gotchas it was carrying are now
+  the skill's, and leaving both would have created exactly the duplicate
+  description this repo has a standing rule against.
+- Added `make skill-check` / `scripts/skill-check.sh` + a pre-commit
+  hook: every command in `.pi/**/*.md` must be a real `make` target, so
+  the Makefile stays the source of truth for invocation and a renamed
+  target fails a commit instead of misleading an agent later. Verified
+  it fails (it caught its own not-yet-created target) and passes.
+- Added the `/e2e` prompt template: promoting a hand-driven
+  `playwright-cli` session into a spec is a transcription with four
+  fixed substitutions (refs → testids, sleeps → `waitForEvent`, raw
+  `window.go` → `callBinding`, short fixture → `LONG_TRACK`), plus three
+  runs — pass, pass again, pass after a DB restore — because the usual
+  failure is a spec depending on state the hand-driving left behind.
+- One shell trap: under `set -euo pipefail`, `x="$(make -pqRr | …)"`
+  fails the whole assignment, because `make -q` exits non-zero when a
+  target is out of date and `pipefail` propagates it.
+
+### Earlier
+
+Phases 1–5 of plan 005: fixture generator and manifest, headless launch
+and seeds, the event bridge + `data-testid` pass + `backend/testctl` +
+`e2e/`, the Vitest component tier + `make bindings-check`, and the
+`events.Emit` wrapper with its in-process service-event tests. Recaps
+and the five "verified end to end" blocks are in
+`.planning/plans/active/005-agent-development-harness.md`; the lessons
+are in `.planning/NOTES.md`.