Consolidate CallbackVector cleanup into free_cbv()

[toddr-bot]

What

Single-owner teardown: free_cbv() now handles all CallbackVector fields, and XML_ParserFree delegates to it instead of duplicating the cleanup inline.

Why

Adding a new SV field to CallbackVector previously required updating two independent cleanup sites — free_cbv() (for early-abort in ParserCreate) and the inline block in XML_ParserFree (for normal teardown). Missing either one leaks memory. This consolidation makes the struct self-cleaning through one function.

How

• Expanded free_cbv() with null-guarded SvREFCNT_dec for every SV handler field (recstring, start_sv through endcd_sv).
• Added a null guard on self_sv so the function is safe for both paths: early-abort (self_sv set) and normal teardown (self_sv already NULL from XML_ParserRelease).
• Replaced the ~70-line inline cleanup block in XML_ParserFree with free_cbv(cbv).
• The six early-abort calls in XML_ParserCreate are unaffected — Newxz zeroes all SV fields, and SvREFCNT_dec(NULL)/Safefree(NULL) are safe no-ops.

Testing

Full test suite passes (make test — all tests OK).

🤖 Generated with Claude Code

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Quality Report

Changes: 1 file changed, 64 insertions(+), 68 deletions(-)

Code scan: clean

Tests: passed (OK)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.06%. Comparing base (ab2416c) to head (5b288c3).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #288      +/-   ##
==========================================
+ Coverage   76.40%   77.06%   +0.66%     
==========================================
  Files           1        1              
  Lines        1102     1112      +10     
  Branches      346      352       +6     
==========================================
+ Hits          842      857      +15     
+ Misses         52       45       -7     
- Partials      208      210       +2     

Flag	Coverage Δ
perl	77.06% <100.00%> (+0.66%)	⬆️
xs	77.06% <100.00%> (+0.66%)	⬆️

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