docs: add CLAUDE.md with Convex performance rules

Encodes the patterns learned from bandwidth optimization so AI coding
assistants get them right from the start — digest owner fields over
users table reads, compound indexes over JS filtering, one-shot fetches
for public pages, change detection in triggers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,36 @@
+# ClawHub — Project Rules
+
+## Convex Performance Rules
+
+- For public listing/browse pages, use `ConvexHttpClient.query()` (one-shot fetch),
+  not `useQuery`/`usePaginatedQuery` (reactive subscription). Reserve reactive
+  queries for data the user needs to see update in real time.
+- Denormalize hot read paths into a single lightweight "digest" table. Every
+  `ctx.db.get()` join adds a table to the reactive invalidation scope.
+- When a `skillSearchDigest` row is available, use `digestToOwnerInfo(digest)`
+  to resolve owner data. NEVER call `ctx.db.get(ownerUserId)` when digest
+  owner fields (`ownerHandle`, `ownerName`, `ownerDisplayName`, `ownerImage`)
+  are already present. Reading from `users` adds the entire table to the
+  reactive read set and wastes bandwidth.
+- Use `convex-helpers` Triggers to sync denormalized tables automatically.
+  Always add change detection — skip the write if no fields actually changed.
+- Use compound indexes instead of JS filtering. If you're filtering docs after
+  the query, you're scanning documents you'll throw away.
+- For search results scored by computed values (vector + lexical + popularity),
+  fetch all results once and paginate client-side. Don't re-run the full search
+  pipeline on "load more."
+- Backfills on reactively-subscribed tables need `delayMs` between batches.
+- Mutations that read >8 MB should use the Action → Query → Mutation pattern
+  to split reads across transactions.
+
+## Convex Conventions
+
+- All mutations import from `convex/functions.ts` (not `convex/_generated/server`)
+  to get trigger wrapping. Type imports still come from `convex/_generated/server`.
+- NEVER use `--typecheck=disable` on `npx convex deploy`.
+- Use `npx convex dev --once` to push functions once (not long-running watcher).
+
+## Testing
+
+- Tests use `._handler` to call mutation handlers directly with mock `db` objects.
+- Mock `db` objects MUST include `normalizeId: vi.fn()` for trigger wrapper compatibility.