feat: model lists and prices that follow each AI tool, a Settings tab per tool, live lane status (#40)

Pricing: the LiteLLM sync now adds every current Claude / GPT (>= 5) /
Gemini (>= 3) chat model before it is used and keeps its own rows
(model_pricing.source = 'sync', the Auto badge) at the published rate. A
user's row (any PUT) and a deleted pattern (model_pricing_dismissed) are
never touched; a deleted built-in row is not re-seeded at the next start; a
reset re-applies the list at once; retired Claude models are priced only
once used.

Models: GET /api/ai-tools/:id/models reads each tool's own list (Codex's
models_cache.json, Claude's aliases named after the newest version plus
priced versions, a catalog tool's vendor rows plus the models its sessions
used). A catalog `model: {flag, vendor?}` field passes `<flag> <id>`
(validated: never a flag or shell text); a per-tool default model starts
each run, and a resume keeps the session's own model.

Settings: every installed, enabled catalog tool without its own tab gets
one (AiToolConfig.tsx): path, homepage, Update, sessions/cost/lanes,
default model, vendor pricing, and the config files its release catalog
lists, edited over the opened sha, syntax-checked, backed up, written
atomically; credential-looking names refused. Antigravity keeps its hooks
card there.

Lanes: a just-started run no longer reads "dead" (age counts the run's
start while the old session is still bound); a second dashboard on the
same database re-broadcasts the lanes the other changed (PRAGMA
data_version, every 2 s); a lane start with a bad model answers 400.

DB: every migration runs under a cross-process lock (<db>-migrate.lock), so
two dashboards started at once on a fresh database both come up.

client/README.md

@@ -204,7 +204,7 @@ client/
 │   │   ├── ActivityFeed.tsx  # Real-time event log; row click expands payload; Session btn navigates
 │   │   ├── Workflows.tsx
 │   │   ├── Settings.tsx
-│   │   ├── AntigravityConfig.tsx  # Settings → Antigravity: Gemini pricing + Antigravity hooks
+│   │   ├── AiToolConfig.tsx  # Settings → <tool>: the generic tab of every installed, enabled catalog tool (path, Update link, sessions/cost/lanes, default model, vendor pricing, catalog-declared config files; Antigravity adds its hooks card)
 │   │   └── NotFound.tsx
 │   │
 │   ├── lib/                # Core utilities & business logic