fix(api): round-trip repeat times attribute

[webern]

Summary

A <repeat> lost its times count on api round-trip. BarlineData carried only a
bool repeat, so the barline reader discarded the count and the writer never emitted it.

Added BarlineData::repeatTimes (an int where 0 means not specified, mirroring the
existing endingNumber convention on the same struct). The barline reader now reads
repeat()->times(), and the barline writer emits times when the count is set. The
common no-times case stays at 0 and nothing is written.

Testing

• New rightBarlineRepeatTimes MeasureWriter test: a backward repeat with
  repeatTimes = 5 emits a <repeat> carrying times="5"
• Full unit suite passes (4334 assertions in 320 test cases)
• Corpus api round-trip regression: 121 passed, 0 failed (up from 119).
  lysuite/ly45a_SimpleRepeat.xml and lysuite/ly45c_RepeatMultipleTimes.xml now
  round-trip and are pinned in the baseline.

References

• Closes api: round-trip drops repeat times attribute #271
• Split from api: round-trip drops modeled attributes (clef @number, repeat @times, key cancel @location, credit-words @justify) #230 · Part of api: expand corpus coverage of the api round-trip pass-list #208 · feeds api: implement ranked fixes and grow the round-trip corpus baseline #213

[github-actions]

Coverage report

Core-dev coverage src/private/mx/core/

Metric	Coverage	Covered / Total
Lines	77.8%	28487 / 36624
Functions	74.3%	6349 / 8550
Branches	50.6%	22632 / 44725

API coverage src/private/mx/{api,impl,utility}/

Metric	Coverage	Covered / Total
Lines	78.4%	6029 / 7687
Functions	63.7%	2045 / 3209
Branches	47.6%	5112 / 10733

Core HTML report | API HTML report

Commit 9fe0f61b3e5ebfbdc1c2ead4c434a41b0e193df9.

[github-actions]

gen-quality gen/

gen-quality: 84.5 / 100   (floor 84.5, +0.0)

  structure     86.5  x0.50   [fn 90.5 / file 82.6]
  cyclomatic    88.4  x0.25
  cognitive     76.6  x0.25

  409 functions across 31 files, 7702 lines (largest file 1044)
  max cc 56  max cognitive 44  max fn loc 152

Worst offenders (top 5 per axis; full lists in score.json):
  cyclomatic gen/xsd/analyze.py:311     report                             56
  cyclomatic gen/plates/build.py:956    _validate_config_against_ir        35
  cyclomatic gen/press/context.py:145   plate_context                      34
  cyclomatic gen/__main__.py:46         _ir                                23
  cyclomatic gen/tests/test_ir.py:102   _check_references                  20
  cognitive  gen/xsd/analyze.py:311     report                             44
  cognitive  gen/ir/resolve.py:119      flat_elements                      40
  cognitive  gen/tests/test_ir.py:102   _check_references                  38
  cognitive  gen/press/context.py:145   plate_context                      37
  cognitive  gen/xsd/analyze.py:207     _sccs                              37
  size       gen/xsd/analyze.py:311     report                             152
  size       gen/press/context.py:145   plate_context                      96
  size       gen/plates/build.py:533    _value_plate                       89
  size       gen/plates/build.py:956    _validate_config_against_ir        89
  size       gen/ir/resolve.py:119      flat_elements                      78

Commit 9fe0f61b3e5ebfbdc1c2ead4c434a41b0e193df9.