feat: model all pedal types in mx::api

[webern]

Human Summary

Changes the way pedals are modeled into two different things. Pedal marks, which are the old fashioned Ped and * marks, and a separate type for more modern lines.

Summary

DirectionReader::parsePedal handled only PedalType start/stop and silently dropped
sostenuto, change, continue, discontinue, and resume, even though core::PedalType
carries all seven tags. This was the last unmodeled item in #324.

The shape decision (called for in #324) was to store the pedal type as one fact in one field
rather than scatter it across start/stop/other vectors. This replaces the pedalStarts /
pedalStops spanner vectors on DirectionData with a single std::vector<PedalData> pedals,
where each PedalData carries a PedalKind enum covering every pedal-line type. Each pedal event
stands on its own and is placed at its own tick, so the model has no neighbor-dependent meaning.

• New PedalData.h: the PedalKind enum (start, stop, sostenuto, change, continueLine,
  discontinue, resume) and the PedalData struct.
• Reader: line pedals (line="yes", plus the inherently line-formatting types
  sostenuto/change/continue/discontinue/resume) go to pedals; sign start/stop still
  route through MarkData as MarkType::pedal / damp, unchanged.
• Writer: a single emitPedal maps PedalKind back to core::PedalType, emits line="yes", and
  emits nothing for an unspecified kind.

Only two corpus files use these types (lysuite/ly31a_Directions.xml, lysuite/ly33a_Spanners.xml)
and both fail first on unrelated features, so this does not flip any file to PASS. It is validated
by a focused unit test that round-trips each pedal type through the api.

This is a breaking change: it reshapes DirectionData's pedal fields.

Testing

• New PedalAllKinds round-trips all seven pedal types through the api; PedalPlacement covers
  placement (*Pedal*: 44 assertions in 5 test cases)
• Full unit suite passes (5130 assertions in 451 test cases)
• api round-trip regression unchanged (284 passed, 0 failed of 284 pinned)

References

• Closes api: many direction-type subtypes are unmodeled stubs (percussion, metronome extras, harp-pedals, scordatura, ...) #324 (the symbol item from that worklist is tracked separately by Proposal: Support Interleaved Words and Symbols in mx::api Directions #294 and is not
  included here)
• Follows the merged direction-type stack feat: model damp, damp-all, eyeglasses, string-mute, and staff-divide directions #358–feat: model the metronome-note form and beat-unit-tied #363
• Part of api: expand corpus coverage of the api round-trip pass-list #208
• Spanner-numbering context: feat: unified spanner numbering with writer-side assignment #320, fix: scope spanner number pools to the part, not the staff #351