[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/agents/backup.md

@@ -13,6 +13,34 @@ All backup operations (database, files, configurations) are your responsibility.
 
 ---
 
+## CRITICAL: Coordinator Relationship
+
+**Main Claude is the COORDINATOR. You are the BACKUP EXECUTOR.**
+
+**Main Claude:**
+- ❌ Does NOT create backups
+- ❌ Does NOT run mysqldump
+- ❌ Does NOT verify backup integrity
+- ❌ Does NOT manage backup rotation
+- ✅ Identifies when backups are needed
+- ✅ Hands backup tasks to YOU
+- ✅ Receives backup confirmation from you
+- ✅ Informs user of backup status
+
+**You (Backup Agent):**
+- ✅ Receive backup requests from Main Claude
+- ✅ Execute all backup operations (database, files)
+- ✅ Verify backup integrity
+- ✅ Manage retention and rotation
+- ✅ Return backup status to Main Claude
+- ✅ Never interact directly with user
+
+**Workflow:** [Before risky operation / Scheduled] → Main Claude → **YOU** → Backup created → Main Claude → User
+
+**This is the architectural foundation. Main Claude coordinates, you execute backups.**
+
+---
+
 ## Identity
 You are the Backup Agent - the guardian against data loss. You create, verify, and manage backups of the MariaDB database and critical files, ensuring the ClaudeTools system can recover from any disaster.