fix: clean windows onboarding with reviewed fixes

Cherry-pick the windows onboarding flow from AnrokX PRs #796 and #791
with all review issues fixed:

Features ported:
- First-run dependency wizard (Git, Node, npm, gh, Claude, Codex)
- Setup action service with PowerShell command runner
- GitHub CLI device-flow login with code detection
- Git identity configuration (name/email)
- Diagnostics panel enhancements
- Toast notification CSS rewrite
- Workspace startup race condition fix (workspaceSystemReady gate)
- Desktop launch trace support in bootstrap page

Issues fixed from review:
- Remove dead `guidance` variable (~60 lines never rendered in template)
- Add retention limit (50 runs) to setupActionService Maps (memory leak)
- Disable updater plugin instead of empty pubkey (prevents silent update failures)
- Keep stderr on non-Windows platforms for debugging (was nulled everywhere)
- Document autoCreate behavioral change in workspaceManager
- Exclude binary artifacts (zip files) and patch script from cherry-pick

Based on work by AnrokX in PRs #796 and #791.

Co-Authored-By: AnrokX <anrokx@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people

CODEBASE_DOCUMENTATION.md

@@ -538,5 +538,16 @@ LOGGING:      Winston-based structured logging with rotation
 9. **Mixed-repo workspaces**: Terminal naming must avoid conflicts between repos
 10. **Template validation**: Always validate workspace templates against schemas
 
+
+## First-Run Dependency Onboarding (Windows)
+
+```
+server/setupActionService.js     - Defines setup actions and launches PowerShell installers
+server/index.js                  - Routes: GET /api/setup-actions, POST /api/setup-actions/run
+client/app.js                    - Guided dependency onboarding steps + diagnostics integration
+client/index.html                - Dependency onboarding modal markup + launch button
+client/styles.css                - Dependency onboarding progress/step styling
+```
+
 ---
 🚨 **END OF FILE - ENSURE YOU READ EVERYTHING ABOVE** 🚨