The make-room enabler: a ModifyEvent that moves a metric event's span
(different Musical position or duration) is now applied to the graph and the
owning voice re-sorted by ascending position (id-tiebroken, the order an
insert maintains), so invariant 3 (VoiceEventsSortedNonOverlap) holds. The
deferral documented in DECISIONS.md is lifted.
modify_event computes one sanction — the move is a valid metric move
(PlacementVerdict::Moved) and the replacement is well-formed — and uses it to
gate both the graph mutation (graph_replace_event) and the voice_occupancy
update, so the canonical index and the graph never diverge. The verdict is
read from voice_occupancy, the graph-independent placement index, so reduce()
and reduce_onto() agree on it; a move with a non-positive span or one that
would overlap a live sibling is refused as a clean NoOp(EventDurationInvalid)
rather than skipped silently. A non-metric move stays deferred, and a
malformed (empty) pitched replacement is neither materialized nor allowed to
move occupancy.
Tests: trim frees the voice slot (a later insert fits); a move onto a sibling
is refused; a trim materializes in the graph (reduce_onto, invariants hold);
a non-metric event is not rewritten onto the musical grid; a malformed move
does not free the slot.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NAtEiJtt9yKVV1zjKYmZhS
Levi Neuwirth
b3403c1d6a