chore: improve docs and remove stale state

[webern]

Summary

The agents left behind a lot of stateful comments and files. This cleans them up and provides a better entrypoint for new agents.

References

• Cleans up after add support for musicxml 4.0 in mx::core #169
• Progresses mx::core Support a newer version of MusicXML #58

[github-actions]

gen-quality gen/

(no report produced)

Commit 32252509139e1aa1956c117227617571c16dbf6e.

[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 c5714a959159614b47bcbe983409cf507d563e28.

[github-actions]

Coverage report

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

Metric	Coverage	Covered / Total
Lines	77.9%	28505 / 36590
Functions	74.4%	6354 / 8542
Branches	50.7%	22645 / 44673

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

Metric	Coverage	Covered / Total
Lines	68.7%	4734 / 6895
Functions	54.8%	1475 / 2692
Branches	40.3%	3848 / 9556

Core HTML report | API HTML report

Commit c5714a959159614b47bcbe983409cf507d563e28.