[gouyt13]

Summary

Known support files currently fall through to full C++/Python/wheel validation. Classify issue templates and CODEOWNERS as metadata, the homepage plotter as Python quality work, example shell runners as ShellCheck work, and core consumer fixtures as C++ checks. Recognize retired example paths when they appear as deletions in complete diffs.

Align lint jobs with those selections: check the homepage plotter and sample runners when present, without failing on a legitimate deletion. Update routing documentation and regression coverage.

Preserve full validation for classifier implementation/test changes, unknown paths, detection failures, release tags/manual builds, and unreleased main versions. Required check names and release logic are unchanged. This PR itself intentionally still requests full CI. Separate agent workflow templates are excluded.

Testing

• New routing regressions fail against the original classifier; 24 routing/release tests and 50 subtests pass after the fix.
• Project Python checks, focused Ruff, ShellCheck, strict MkDocs, YAML parsing and diff checks passed.
• Executed the actual lint commands in isolated fixtures with optional files present and deleted; both cases pass.
• Independent review found a missing-file lint false failure; corrected it and obtained a final local review PASS.

Cloud CI and platform builds have not run on this branch yet. actionlint was unavailable; YAML syntax and command wiring were checked locally. MkDocs emitted the existing Material advisory about MkDocs 2.0.