Introduces a shared `toolTargeting.ts` module that resolves the active MIDI
region/track from the user's current selection, enabling tools to operate on
the correct target without requiring explicit track IDs in most cases.
Adds two new read-only tools — `list_all_tracks` and
`get_user_selected_music_range_and_track` — so the agent can inspect
available tracks and the current selection context before acting.
Also refactors `AddNotesTool` to auto-create MIDI regions when no region
exists, refactors `RemoveNotesTool`, `ReadMusicTool`, and
`ReadChordProgressionTool` to use the new targeting helpers, adds a
`buildToolHistoryContent` hook to `BaseTool` for cleaner chat history
display, and updates system prompts and tests throughout.
Xiaohan-Tian