BeatForge 0.2.4

Reliability: undo now fully restores removed tracks (automation lanes, inbound sends, all patterns), removed device slots, and note order. Tone clock allowed to run in a worker. Visible error when a project file cannot be opened. Save dialog titled BeatForge. Internals: user-journey test harness (Playwright) and a 69-command undo/redo invariant now gate releases.