fix(experimental/seclang): resolve golangci-lint failures in parser_v2

[Copilot]

Four lint violations introduced in the experimental ANTLR4 parser were breaking CI (golangci-lint via gocritic + unused checks).

Changes

• Remove unused const maxIncludeRecursion — declared but never referenced
• Remove unused Parser.includeCount field — never read or written
• Remove unused typeConverter.errors field — never populated or consumed
• Fix appendAssign (gocritic) — replace single-line cross-slice append with two-statement form so the result is assigned back to the same slice variable:

// before — triggers appendAssign warning
allErrors := append(lexerErrorListener.errors, parserErrorListener.errors...)

// after
allErrors := lexerErrorListener.errors
allErrors = append(allErrors, parserErrorListener.errors...)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.25%. Comparing base (0f454fb) to head (c232e96).
⚠️ Report is 6 commits behind head on feature/experimental-seclang.

Additional details and impacted files

@@                      Coverage Diff                      @@
##           feature/experimental-seclang    #1501   +/-   ##
=============================================================
  Coverage                         82.24%   82.25%           
=============================================================
  Files                               176      176           
  Lines                              9228     9229    +1     
=============================================================
+ Hits                               7590     7591    +1     
  Misses                             1324     1324           
  Partials                            314      314           

Flag	Coverage Δ
coraza.rule.case_sensitive_args_keys	82.21% <100.00%> (+<0.01%)	⬆️
coraza.rule.mandatory_rule_id_check	82.24% <100.00%> (+<0.01%)	⬆️
coraza.rule.multiphase_evaluation	81.99% <100.00%> (+<0.01%)	⬆️
coraza.rule.no_regex_multiline	82.24% <100.00%> (+<0.01%)	⬆️
default	82.25% <100.00%> (+<0.01%)	⬆️
examples+	16.64% <ø> (ø)
examples+coraza.rule.case_sensitive_args_keys	82.15% <100.00%> (+<0.01%)	⬆️
examples+coraza.rule.mandatory_rule_id_check	82.24% <100.00%> (+<0.01%)	⬆️
examples+coraza.rule.multiphase_evaluation	81.80% <100.00%> (+<0.01%)	⬆️
examples+coraza.rule.no_regex_multiline	82.09% <100.00%> (+<0.01%)	⬆️
examples+memoize_builders	82.18% <100.00%> (+<0.01%)	⬆️
examples+no_fs_access	80.03% <100.00%> (+<0.01%)	⬆️
ftw	82.25% <100.00%> (+<0.01%)	⬆️
memoize_builders	82.34% <100.00%> (+<0.01%)	⬆️
no_fs_access	81.81% <100.00%> (+<0.01%)	⬆️
tinygo	82.22% <100.00%> (+<0.01%)	⬆️

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