fix: add automatic temp folder cleanup at Maestro startup

Problem:
When AutoForge runs agents that use Playwright for browser testing or
mongodb-memory-server for database tests, temporary files accumulate in
the system temp folder (%TEMP% on Windows, /tmp on Linux/macOS). These
files are never cleaned up automatically and can consume hundreds of GB
over time.

Affected temp items:
- playwright_firefoxdev_profile-* (browser profiles)
- playwright-artifacts-* (test artifacts)
- playwright-transform-cache
- mongodb-memory-server* (MongoDB binaries)
- ng-* (Angular CLI temp)
- scoped_dir* (Chrome/Chromium temp)
- .78912*.node (Node.js native module cache, ~7MB each)
- claude-*-cwd (Claude CLI working directory files)
- mat-debug-*.log (Material/Angular debug logs)

Solution:
- New temp_cleanup.py module with cleanup_stale_temp() function
- Called at Maestro (orchestrator) startup in autonomous_agent_demo.py
- Only deletes files/folders older than 1 hour (safe for running processes)
- Runs every time the Play button is clicked or agent auto-restarts
- Reports cleanup stats: dirs deleted, files deleted, MB freed

Why cleanup at Maestro startup:
- Reliable hook point (runs on every agent start, including auto-restart
  after rate limits which happens every ~5 hours)
- No need for background timers or scheduled tasks
- Cleanup happens before new temp files are created

Testing:
- Tested on Windows with 958 items in temp folder
- Successfully cleaned 45 dirs, 758 files, freed 415 MB
- Files younger than 1 hour correctly preserved

Closes #155

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

autonomous_agent_demo.py

@@ -263,6 +263,17 @@ def main() -> None:
             )
         else:
             # Entry point mode - always use unified orchestrator
+            # Clean up stale temp files before starting (prevents temp folder bloat)
+            from temp_cleanup import cleanup_stale_temp
+            cleanup_stats = cleanup_stale_temp()
+            if cleanup_stats["dirs_deleted"] > 0 or cleanup_stats["files_deleted"] > 0:
+                mb_freed = cleanup_stats["bytes_freed"] / (1024 * 1024)
+                print(
+                    f"[CLEANUP] Removed {cleanup_stats['dirs_deleted']} dirs, "
+                    f"{cleanup_stats['files_deleted']} files ({mb_freed:.1f} MB freed)",
+                    flush=True,
+                )
+
             from parallel_orchestrator import run_parallel_orchestrator
 
             # Clamp concurrency to valid range (1-5)