fix(studio): keep performance keys active across controls

[samohovets]

Summary

• Keep mapped note and octave keys responsive while Studio controls are focused, without intercepting Cmd/Ctrl/Alt shortcuts.
• Release owned performance keys safely across focus, visibility, connection, and transport changes.
• Clarify Studio playback, editing, offline, conflict, rejected, read-only, and computed states with stronger keyboard guidance and focus treatment.
• Expand client coverage for focused controls, modifiers, repeats, lifecycle cleanup, failure paths, and accessibility relationships.

Closes #4.

Changelog

Public summary:

• Studio now keeps mapped performance keys playing while controls are focused, with clearer playback and editing states.

Context:

• Studio is designed to behave as a playable instrument first and a source-backed editor second.
• The mapped A–K note keys and Z/X octave controls remain dominant while Studio is connected, while command shortcuts and non-performance editing keys keep their native behavior.

Verification

• pnpm validate
• pnpm --filter @patchwave/studio test
• pnpm --filter @patchwave/studio typecheck
• pnpm --filter @patchwave/studio build
• Live Chrome playback smoke test with a focused number input