scoreview-engine v4.7.5-engine.3

release v4.7.5-engine.3

Metadata gains keySigs and rehearsalMarks. ScoreView needs the sounding
key including its mode for a start-tone/tonic button, and rehearsal marks
for jumping to "C" in rehearsal navigation. The mode is in no artifact of
the stock CLI (the MIDI key signature always carries mode byte 0), so it
can only come from here.

Both lists are built in src/meta/scoremeta.cpp from the score model; the
MuseScore core stays unpatched. Measures are counted 1-based along the
notated chain, ticks are notated (repeats not unrolled). The corpus
comparison against the frozen Qt baseline allows the two new keys, native
and wasm still compare them exactly.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HR7wyuvffSuWkRYxv9D5kL