docs: add issue tracker to api feature audit

[webern]

Summary

The api-feature-audit doc now doubles as a tracker. Added a Tracker table mapping every audited
item to its GitHub issue or PR, plus a pointer near the top to the parent tracker issue.

The three section-1a enum bugs are marked done against their fix PRs (#177, #178, #179). The
remaining 16 items now have issues (#181-#196), all linked as sub-issues of #159, which was rewritten
into a parent tracker with live checkboxes.

References

• Progresses Analyze and surface differences to the mx/api layer. #159

[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 799cd15d464fa12c5625122aa1b895cb9321ff34.

[github-actions]

Coverage report

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

Metric	Coverage	Covered / Total
Lines	77.9%	28539 / 36619
Functions	74.4%	6360 / 8547
Branches	50.7%	22672 / 44725

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

Metric	Coverage	Covered / Total
Lines	68.7%	4735 / 6896
Functions	54.8%	1475 / 2692
Branches	40.3%	3850 / 9558

Core HTML report | API HTML report

Commit 799cd15d464fa12c5625122aa1b895cb9321ff34.