ci: skip workflows whose inputs did not change

[roivanov]

Summary

Skip Tile, CodeQL, and the naming guard when a change cannot affect what those jobs read. This is one of two independent workflow changes split out of #1397. The other is the main cancellation change.

Changes

• Declare the Tile any_changed filter so a non-Tile diff skips the Tile jobs, while a push with no detectable diff still runs them. The job condition already read any_changed, but dorny/paths-filter only sets an output for a filter that is declared. That name was not declared, so the output stayed empty. Empty is not 'true', and the condition was any_changed != 'true', so it was always true and every Tile job ran on every push.
• Run CodeQL on push and pull request only when Rust, Cargo manifests, .github/, shell, or Python files change. The weekly schedule still scans the whole tree.
• Run the naming guard only for cuda-oxide/crates/, its script, and its workflow. The comment records why cutile-rs and the shared host crates stay out: the script's SEARCH_ROOTS does not read them.

Testing

Workflow configuration only. No crate, example, or guard behavior changed, so just check and cargo oxide run were not run.

• just -f cuda-oxide/Justfile check passes (the local mirror of CI: fmt, clippy, tests, guards, docs)
• cargo oxide run <example> passes, or cuda-oxide/scripts/smoketest.sh -o '^<example>$'
• New example added (if applicable)

Checklist

• All commits signed off (git commit -s)
• SPDX headers on new source files

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[roivanov]

Duplicate of #1397, which now contains only this path-filter change. The main cancellation change is #1399.