docs: note Realtime waitFor 10s timeout in CLAUDE.md

Documents the flake fix from 3afc911 so future contributors don't
accidentally drop the timeout back to 5s. Cross-referenced with the
`project_realtime_config` memory, which has the full rationale.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -100,6 +100,7 @@ just test-e2e-headed     # Playwright with visible browser (debugging)
 - `packages/test-utils/src/realtime-helpers.ts` — `subscribePostgresChanges(client, opts)` with `waitFor(predicate, ms)` — awaits SUBSCRIBED handshake, dedups events, leaks nothing between tests
 - Vitest unit harness in `apps/web/` — `vitest.config.ts` (jsdom env) + `vitest.setup.ts` (fake-indexeddb/auto) + `pnpm --filter @colectivo/web test:unit`
 - Realtime config gotchas documented in `project_realtime_config` memory: tenant name, DB_USER=supabase_admin, `SEED_SELF_HOST: "true"`, pre-created `realtime` schema, publication + REPLICA IDENTITY FULL
+- **Realtime `waitFor` timeout is 10s, not 5s.** Under full `just test-all` load the Phoenix socket occasionally takes several seconds to propagate a fresh subscription's filter before the test mutation fires. Set in `packages/test-utils/src/realtime-helpers.ts`. Don't drop below 10s — passing runs resolve on event arrival, only the flake window widened.
 
 ### Fase 2a — what has been built