feat(editor): bulk barline locks + band-aware Tempo Map selection

[ChrisBeWithYou]

What this is

PR 3 of the #285 re-cut (stacked on #290 → #289 → main; retarget as parents merge; CI fires on retarget to main — local gates green). The marquee-reliability and bulk-lock features, rebuilt on main's existing multi-select infrastructure.

The features

• Bulk locks, one undo. TempoLockCmd makes lock/unlock a first-class exec/rollback command: select any number of barlines (marquee, Shift-click, Ctrl/Cmd-click, Ctrl/Cmd+A — uncapped) and the S key / toolbar button / right-click menu applies one uniform state (lock all unless every one is already locked) as one undoable edit. Entries re-resolve by time so undo survives a grid rebuild.
• sessionNeutral history flag (new, in history.js): lock toggles belong in Undo but are an editor preference, not pack data — they now skip markSessionDirty, so locking barlines never creates a false Save prompt. _afterEdit(cmd) threads the command through exec/undo/redo.
• Band-aware selection. The marker lane splits into a top handle band (direct edits: forgiving 8px pole grabs, sub-beat rubato) and the lane body below (marquee territory) — while the thin full-height barline keeps a precise 2.5px drag target anywhere, and holding a selection modifier restores the forgiving width. Hover mirrors the exact same tolerance so the cursor never promises a grab the click would route to the marquee.
• Ctrl/Cmd-click toggles individual poles in/out of the selection (returns a new Set — no shared-reference mutation). Marquee finalize routes through a pure selector that focuses the drag end (forward drag → last hit, reverse → first).
• Group-aware chrome: the toolbar lock button's face derives from the same plan the verb executes ("Lock 12 barlines"), the inspector label shows "N barlines selected · Shift-click extends · Ctrl/Cmd-click toggles", and right-clicking outside the selection collapses to the clicked barline before showing verbs.

What was already on main (not re-ported)

The marquee drag machinery, Shift-click range extend, Ctrl/Cmd+A select-all, Escape-clears, and group drag all landed in the earlier multi-select wave — this PR layers planners + the undo command + the hit-band refinement on top.

Tests

8 new cases in tests/tempo_multiselect.test.mjs: the handle band, the dual grab tolerance, marquee replace/extend + drag-end focus, non-mutating Ctrl-toggle, the uniform lock plan (mixed → lock-all; all → unlock-all; single-focus fallback), the no-cap contract (512 barlines), the button-face pure, and the full exec → one-undo → redo round-trip asserting S.sessionDirty === false. (The shared test env's fake elements gained no-op classList — the signpost cue path needed it.)

Gates: 182 JS suites green, pytest 291/2 skipped, lint 0 errors / 3 baseline warnings.

Remaining from the salvage queue

Tracks lanes UI → engine/meters (evaluate).

🤖 Generated with Claude Code

https://claude.ai/code/session_01EBQCHCNA81E9tHmSDHSe2Q

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