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/prompts/e2e.md

@@ -0,0 +1,55 @@
+---
+description: Promote a hand-driven playwright-cli session into a committed spec in e2e/
+argument-hint: "[name of the flow]"
+---
+Promote the flow I just drove by hand into a committed Playwright spec.
+Flow: ${@:-infer it from the playwright-cli commands in this session}
+
+This is a transcription with fixed substitutions, not a fresh test.
+Work from what actually happened in this session, not from what the UI
+looks like it should do.
+
+**1. Recover the flow.** List the `playwright-cli` calls made this
+session, in order, and the assertion each one was really checking. Then,
+before writing anything, ask the running app what fired:
+
+```
+playwright-cli -s=yj eval "() => window.__yjEvents.names()"
+```
+
+Await the events that are actually in that list. Do not guess event
+names from `backend/events/`.
+
+**2. Substitute, one for one.**
+
+- `click e15` → a role or `data-testid` selector. Snapshot refs are
+  per-snapshot and meaningless in a spec. If the only stable selector
+  would be structural, add a `data-testid` to the Lit component and
+  re-run `make ui-test`.
+- any sleep, or "it looked settled" → `waitForEvent(app, 'X')`.
+- `window.go.…` → `callBinding(app, path, args)`, which times out.
+- a short fixture track → `LONG_TRACK`, if the flow needs playback to
+  still be running on the next line. Every other fixture is 2–6 s.
+- `getByRole('button', { name })` → add `exact: true`.
+
+**3. Place it.** `e2e/specs/<area>.spec.ts`, importing `test`, `expect`
+and the helpers from `../support/fixtures.js` — never `@playwright/test`
+directly. Match the surrounding specs' comment style: say what the test
+is protecting against, not what the lines do.
+
+**4. Prove it is a spec and not a recording.** Three runs, in order:
+
+```
+make e2e E2E_ARGS='--grep "<name>"'    # it passes
+make e2e E2E_ARGS='--grep "<name>"'    # again — catches dependence on
+                                       #   state the first run left
+```
+
+then once more after restoring the database through `/__test/`, which
+catches dependence on state *my hand-driving* left behind — the single
+most likely way a promoted spec passes here and fails in CI. Leave the
+database as you found it: snapshot/restore, or reset in `beforeEach`.
+
+**5. Then the whole suite:** `make e2e`. If the promotion turned up a
+new trap, append it to `.planning/NOTES.md`; if it turned up a bug,
+tell me rather than asserting the broken behaviour.