Option<Selection> becomes a paint-ordered set with an anchor member.
click replaces, toggle_at adds/removes (anchor = last added), select_within
takes the hit-test within(rect) in paint order deduped by score object —
a ledgered note's synthesized ledger strokes collapse into its notehead's
member, the representative id preferring the non-synthesized occurrence so
relayout cannot wrongly drop it. Single-target intents retarget to the
anchor, byte-identical at N=1. delete_selection batches atomically via one
transaction (a refused member rolls back the whole batch);
alter_selection instead mints ONE TransposeIntervalOp naming every target —
the format's native atomic multi-target primitive
(req:opcat:transpose-interval-atomic) — preserving N=1 op-stream
compatibility outright. Anchor fallback across relayout: next surviving
member after the anchor's original position, wrapping. Four mutations
killed and coordinator re-verified.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Levi Neuwirth
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