feat: report non-fatal translation diagnostics

[webern]

Summary

Adds an optional Diagnostics collector to the getScore, intoScore, and fromScore translation APIs. Callers can inspect reports after a call or receive them synchronously through a handler while fatal failures remain in Result.

The first reports cover two existing recoveries: an out-of-range time-signature staff number being applied to all staves, and an octave-shift stop with no matching start using the MusicXML default size of 8. Diagnostics carry score locations and have a canonical formatter. More than 16 concurrent numbered spanners remains fatal, but now returns a located tooManyElements error instead of an unlocated internal error.

Testing

• Diagnostics tests: 55 assertions in 7 test cases
• make api-test: 5580 assertions in 617 test cases
• make api-roundtrip: 414 passed, 0 failed
• make test-all
• make wasm-test
• make fmt

References

• Progresses Consider a different error or warning mechanism. #432
• Stacked on feat: carry structured location and exception cause in api errors #436; merges after it