Hide console window, add Debug Window tray option

- Hide console window by default (windows_subsystem = "windows")
- Add "Show Debug Window" menu item to tray
- AllocConsole when debug window requested
- Console shows logs for troubleshooting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

agent/Cargo.toml

@@ -72,6 +72,7 @@ windows = { version = "0.58", features = [
     "Win32_System_LibraryLoader",
     "Win32_System_Threading",
     "Win32_System_Registry",
+    "Win32_System_Console",
     "Win32_Security",
     "Win32_Storage_FileSystem",
 ]}