Fix Remote keyboard shortcut injection

[enaboapps]

Summary

• map canonical A-Z and 0-9 protocol keys to physical Windows key events
• omit modifiers already held by the Remote session from shortcut press and release
• preserve standalone shortcuts and macOS layout-dependent key handling
• clean up successfully pressed shortcut keys after partial injection failures

Root cause

Remote already sends the PC's canonical payload, for example keys: ["Ctrl", "A"]. Enigo's Windows conversion kept the Shift-state byte returned for uppercase Unicode characters and treated the combined value as a virtual-key code. PC also replayed Ctrl inside the shortcut even though keyboard.modifierDown already held it.

Validation

• npm run lint
• npm test (74 Vitest tests and 5 release-feed tests passed)
• npm run build
• cargo fmt --manifest-path src-tauri/Cargo.toml --check
• cargo clippy --locked --manifest-path src-tauri/Cargo.toml --all-targets -- -D warnings
• cargo test --locked --manifest-path src-tauri/Cargo.toml (217 unit tests and 2 config tests passed)
• npm run tauri build -- --bundles nsis --no-sign
• Remote src/remote/RemoteSession.test.ts (12 tests passed)

Physical Windows and macOS shortcut checks remain for release validation.

Closes #647