fix: Supabase telemetry security lockdown (v0.11.16.0) (#460)

* fix: drop all anon RLS policies + revoke view access + add cache table

Migration 002 locks down the Supabase telemetry backend:
- Drops all SELECT, INSERT, UPDATE policies for the anon role
- Explicitly revokes SELECT on crash_clusters and skill_sequences views
- Drops stale error_message/failed_step columns (exist live but not in migration)
- Creates community_pulse_cache table for server-side aggregation caching

* feat: extend community-pulse with full dashboard data + server-side cache

community-pulse now returns top skills, crash clusters, version distribution,
and weekly active count in a single aggregated response. Results are cached
in the community_pulse_cache table (1-hour TTL) to prevent DoS via repeated
expensive queries.

* fix: route all telemetry through edge functions, not PostgREST

- gstack-telemetry-sync: POST to /functions/v1/telemetry-ingest instead of
  /rest/v1/telemetry_events. Removes sed field-renaming (edge function expects
  raw JSONL names). Parses inserted count — holds cursor if zero inserted.
- gstack-update-check: POST to /functions/v1/update-check.
- gstack-community-dashboard: calls community-pulse edge function instead of
  direct PostgREST queries.
- config.sh: removes GSTACK_TELEMETRY_ENDPOINT, fixes misleading comment.

* test: RLS smoke test + telemetry field name verification

- verify-rls.sh: 9-check smoke test (5 reads + 3 inserts + 1 update)
  verifying anon key is fully locked out after migration.
- telemetry.test.ts: verifies JSONL uses raw field names (v, ts, sessions)
  that the edge function expects, not Postgres column names.
- README.md: fixes privacy claim to match actual RLS policy.

* chore: bump version and changelog (v0.11.16.0)

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

* fix: pre-landing review fixes — JSONB field order, version filter, RLS verification

- Dashboard JSON parsing: use per-object grep instead of field-order-dependent
  regex (JSONB doesn't preserve key order)
- Version distribution: filter to skill_run events only (was counting all types)
- verify-rls.sh: only 401/403 count as PASS (not empty 200 or 5xx); add
  Authorization header to test as anon role properly
- Remove dead empty loop in community-pulse

* chore: untrack browse/dist binaries — 116MB of arm64-only Mach-O

These compiled Bun binaries only work on arm64 macOS, and ./setup
already rebuilds from source for every platform. They were tracked
despite .gitignore due to being committed before the ignore rule.
Untracking stops them from appearing as modified in every diff.

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

* docs: tone down changelog — security hardening, not incident report

* fix: keep INSERT policies for old client compat, preserve extra columns

- Keep anon INSERT policies so pre-v0.11.16 clients can still sync
  telemetry via PostgREST while new clients use edge functions
- Add error_message/failed_step columns to migration (reconcile repo
  with live schema) instead of dropping them
- Security fix still lands: SELECT and UPDATE policies are dropped

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

* fix: sync package.json version with VERSION file (0.11.16.0)

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>