merge: incorporate origin/main into community-mode branch

Conflicts resolved:
- README.md: merge skill lists — keep /gstack-submit from our branch,
  add /plan-devex-review, /devex-review, /pair-agent from main. Accept
  main's team mode step 2 text.
- setup: keep both our install ping (step 9) and main's team mode
  hook registration (step 10)
- supabase/functions/telemetry-ingest/index.ts: keep our deletion
  (dead code removed earlier on this branch, main modified it)

Main brought in: team mode (--team flag, auto-update hook, session
tracking), /plan-devex-review + /devex-review skills, /pair-agent
skill, open-gstack-browser, /checkpoint, /health, /humanizer.

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

.gitignore

@@ -1,5 +1,6 @@
 .env
 node_modules/
+dist/
 browse/dist/
 design/dist/
 bin/gstack-global-discover
@@ -7,6 +8,11 @@ bin/gstack-global-discover
 .claude/skills/
 .agents/
 .factory/
+.kiro/
+.opencode/
+.slate/
+.cursor/
+.openclaw/
 .context/
 extension/.auth.json
 .gstack-worktrees/