docs: record deploy procedure, update-flow architecture, and data-model quirks

CLAUDE.md

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+# ytplayer — project facts for agents
+
+## What this is
+Ad-free YouTube player. Three shells share `frontend/`: **web PWA** (Bun + Hono in
+`server/`, the production deployment), Tauri (Windows), zero-native (Linux/macOS).
+The PWA is what runs in production; `legacy/` holds the old native-only docs.
+
+## Production deployment (web PWA)
+- URL: **https://worship.hesed.sbs** (Traefik label in `docker-compose.yml`)
+- Runs on the **homelab** Dokploy remote node; control plane is Dokploy on the VPS
+  (`193.160.119.172`, API key in `~/development/.secrets/dokploy-api.env`).
+- Compose ID: **`wprYCM8T51f7JtSHb983p`** (project `ytplayer`, env `production`).
+- **Pushing to git does NOT deploy.** Trigger explicitly (build ≈ 5–6 min):
+  ```bash
+  ssh -i ~/.ssh/tmp_vps/dokploy_session root@193.160.119.172 \
+    "curl -s -X POST -H 'x-api-key: $KEY' -H 'Content-Type: application/json' \
+     -d '{\"composeId\":\"wprYCM8T51f7JtSHb983p\"}' http://localhost:3000/api/compose.deploy"
+  # poll composeStatus via /api/compose.one?composeId=... until done|error
+  ```
+- Confirm the deploy landed: `curl https://worship.hesed.sbs/api/version` — the
+  `buildTag` (content hash of every file under `./public`) must change.
+- Homelab node is NOT always reachable on LAN; SSH via the VPS hop:
+  `ssh root@193.160.119.172` → `ssh root@10.8.0.2` (WireGuard). Container name:
+  `ytplayer-main-1dihzn-ytplayer-1`. DB: libsql file `/app/data/ytplayer.db`
+  (query with `docker exec <c> bun -e '...' `using `@libsql/client`).
+
+## Update-flow architecture (fragile — read before touching)
+- `GET /sw.js` is served by the server with the real `BUILD_TAG` **injected by
+  regex** over the fallback expression in `frontend/sw.js`. Never switch back to
+  an exact-string replace: when the fallback literal was bumped (`v1.0.3`→`v1.0.4`)
+  the exact match silently failed, the SW version froze, and **no client ever
+  received another update** while `/api/version` kept announcing one — the
+  "Update available keeps showing" bug.
+- `BUILD_TAG` hashes **every** file under `./public` recursively. Don't reduce it
+  to a file subset; a change to an unlisted shell file would stop busting caches.
+- The update banner only shows when a waiting SW exists **and the page already
+  has a controller** — a first install (fresh visit, or after Settings → Force
+  refresh unregisters) passes through `waiting` transiently and must not banner.
+- "Refresh UI" (`frontend/sw-update.js`): if no worker is waiting yet (banner came
+  from the `/api/version` poll), it calls `reg.update()`, waits for `installed`,
+  posts SKIP_WAITING, waits for `controllerchange`, then reloads once.
+
+## Data model quirks
+- Client state persists in localStorage key **`_ytpdata`** and syncs (debounced
+  400 ms) to `POST /api/user/sync`, keyed by a browser fingerprint.
+- **A-B loop markers are per-song-per-playlist**: stored on the playlist's own
+  copy of the video (`entry.ab = {a, b}`) when playback source is that playlist;
+  `data.abMarkers[videoId]` is only the fallback for non-playlist playback.
+
+## Testing
+- Unit: `node --test frontend/` (sw, sw-update, async-guard).
+- E2E: `npx playwright test` — WebKit iPhone-12 profile against a static serve of
+  `frontend/` (needs `npx playwright install webkit`). A spurious update banner
+  will make the settings-panel specs fail with `#modal intercepts pointer events`
+  — that failure mode is a real app bug, not test flake.
+- Test records on prod use `Probe */Recon *` names; clean via the container DB,
+  children (`video_history`) first.
+
+## Commit rules
+One changeset = one commit, single-line imperative message, **no AI attribution
+of any kind** (global rule). `git push origin main` pushes to both remotes.