fix(desktop): preserve main window geometry across toolbar mode

[bobleer]

Summary

• keep temporary toolbar/floating-window bounds out of persisted main-window state
• repair legacy undersized startup geometry to the standard 1200×800 client size and reapply an 800×600 minimum
• persist restored normal geometry across close, quit, restart, tray, and process-exit paths
• use matching inner-size metrics during toolbar round trips to avoid decorated-window growth
• keep the new native geometry command local in remote/peer-device modes

Root cause

Toolbar mode morphs the existing main window into a compact floating surface. The window-state plugin cached those resize and move events, then wrote the floating bounds during shutdown. The next launch restored that transient geometry as if it were the normal client window.

Verification

• pnpm run type-check:web
• focused Web UI tests: 3 files, 71 tests passed
• cargo check -p bitfun-desktop
• cargo test -p bitfun-desktop main_window_geometry_tests --lib
• cargo test -p bitfun-desktop every_registered_command_declares_a_remote_workspace_policy --lib
• cargo test -p bitfun-cli peer_host::dispatch::tests::local_only_commands_are_denied
• cargo build -p bitfun-desktop
• git diff --check

Visuals

Not applicable: this corrects native startup/restoration geometry without changing the rendered UI.

AI-assisted. Testing level: fully tested for the touched paths.