docs(validation): state invariants in comments, not prior behaviour

[simontaurus]

Four comments explained the defect the code was added for rather than what it now guarantees. Once that code is gone the reference is unreadable, and the history belongs in the commit that made the change.

Changes

• select_rules - states that the CLI and the MCP server share it so both answer a query identically, and that unenforced_only selects the population before area narrows it. Drops the account of how the two copies diverged.
• _ADVICE_LEVELS - states that it is enumerated so an unrecognised level is a distinct case rather than one this set absorbs.
• severity - states that the vocabulary grows and the raise is reachable whenever a version is vendored, without naming the keyword that prompted it.
• _read_rules_schema - states that absent and corrupt must stay distinguishable, and what collapsing them would allow.

No behaviour change. 463 validation tests pass, make check exits 0.

[github-actions]

Release preview

No version bump from the current commits (stays at v0.18.0). Use conventional commit types (feat, fix, ...) to trigger a release.

Changelog preview (truncated)

_{Preview via python-semantic-release and conventional commits.}

[github-actions]

📊 Benchmark Results

Click to see benchmark comparison

📊 Benchmark Comparison (threshold: 1.3x)
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➖ Unchanged (within threshold):
  ➖ test_simple_dict_document_store: 0.0017s → 0.0017s (-0.3%)
  ➖ test_sqlite_document_store: 0.0019s → 0.0019s (-0.9%)
  ➖ test_local_sparql_store: 0.0389s → 0.0388s (-0.2%)
  ➖ test_oneof_subschema: 0.0606s → 0.0627s (+3.5%)
  ➖ test_enum_docstrings: 0.0513s → 0.0521s (+1.5%)
  ➖ test_subclass_inheritance: 0.0550s → 0.0566s (+3.0%)
  ➖ test_class_hierarchy: 0.0519s → 0.0536s (+3.2%)
  ➖ test_core[v1]: 0.0388s → 0.0400s (+3.1%)
  ➖ test_core[v2]: 0.0444s → 0.0461s (+3.9%)
  ➖ test_schema_generation[v1]: 0.0017s → 0.0017s (-0.2%)
  ➖ test_schema_generation[v2]: 0.0028s → 0.0028s (-0.7%)
  ➖ test_simple_json: 0.0007s → 0.0007s (-1.4%)
  ➖ test_complex_graph: 0.0016s → 0.0016s (-1.7%)

============================================================
Summary: 0 regressions, 0 improvements, 13 unchanged
============================================================

✅ No significant performance regressions

Threshold: 1.3x (30% slower triggers a regression warning)

Note: Benchmarks are informational only and won't fail the build.

_{💡 Tip: Download the benchmark-results artifact for detailed JSON data}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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