[Config] Add coding guidelines and code-fixer agent

Major additions:
- Add CODING_GUIDELINES.md with "NO EMOJIS" rule
- Create code-fixer agent for automated violation fixes
- Add offline mode v2 hooks with local caching/queue
- Add periodic context save with invisible Task Scheduler setup
- Add agent coordination rules and database connection docs

Infrastructure:
- Update hooks: task-complete-v2, user-prompt-submit-v2
- Add periodic_save_check.py for auto-save every 5min
- Add PowerShell scripts: setup_periodic_save.ps1, update_to_invisible.ps1
- Add sync-contexts script for queue synchronization

Documentation:
- OFFLINE_MODE.md, PERIODIC_SAVE_INVISIBLE_SETUP.md
- Migration procedures and verification docs
- Fix flashing window guide

Updates:
- Update agent configs (backup, code-review, coding, database, gitea, testing)
- Update claude.md with coding guidelines reference
- Update .gitignore for new cache/queue directories

Status: Pre-automated-fixer baseline commit

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.claude/.periodic-save-state.json

@@ -0,0 +1,5 @@
+{
+  "active_seconds": 3240,
+  "last_update": "2026-01-17T19:51:24.350999+00:00",
+  "last_save": null
+}