[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>

FIX_FLASHING_WINDOW.md

@@ -0,0 +1,60 @@
+# FIX: Stop Console Window from Flashing
+
+## Problem
+The periodic save task shows a flashing console window every minute.
+
+## Solution (Pick One)
+
+### Option 1: Quick Update (Recommended)
+```powershell
+# Run this in PowerShell
+.\.claude\hooks\update_to_invisible.ps1
+```
+
+### Option 2: Recreate Task
+```powershell
+# Run this in PowerShell
+.\.claude\hooks\setup_periodic_save.ps1
+```
+
+### Option 3: Manual Fix (Task Scheduler GUI)
+1. Open Task Scheduler (Win+R → `taskschd.msc`)
+2. Find "ClaudeTools - Periodic Context Save"
+3. Right-click → Properties
+4. **Actions tab:** Change Program/script from `python.exe` to `pythonw.exe`
+5. **General tab:** Check "Hidden" checkbox
+6. Click OK
+
+---
+
+## Verify It Worked
+
+```powershell
+# Check the executable
+Get-ScheduledTask -TaskName "ClaudeTools - Periodic Context Save" |
+    Select-Object -ExpandProperty Actions |
+    Select-Object Execute
+
+# Should show: ...pythonw.exe (NOT python.exe)
+
+# Check hidden setting
+Get-ScheduledTask -TaskName "ClaudeTools - Periodic Context Save" |
+    Select-Object -ExpandProperty Settings |
+    Select-Object Hidden
+
+# Should show: Hidden: True
+```
+
+---
+
+## What This Does
+
+- Changes from `python.exe` → `pythonw.exe` (no console window)
+- Sets task to run hidden
+- Changes to background mode (S4U LogonType)
+
+**Result:** Task runs invisibly - no more flashing windows!
+
+---
+
+**See:** `INVISIBLE_PERIODIC_SAVE_SUMMARY.md` for complete details