Cut redundant GitHub Actions usage

[nickhamze]

What changed

• stop repeating the protected Quality matrix after every merge to main
• reserve the Intel runner for compatibility and release-chain changes
• keep manual Quality dispatch as the complete pre-release validation lane
• repair CodeQL's invalid matrix concurrency reference and move source scans to weekly/manual runs
• add regression checks for the budget policy
• update the release guide and repo-backed Wiki

Why

The last week used 57.7 hours of macOS runner time. Redundant post-merge Quality runs accounted for 30.2 hours, while the invalid CodeQL workflow created 47 failed runs. The repository is public, so standard hosted-runner billing is currently zero, but this removes the excess Actions volume and protects the budget if that changes.

Validation

• actionlint 1.7.12 on the changed workflows
• shellcheck on the classifier self-test
• CI classifier and workflow policy self-test
• repo-backed Wiki validation
• YAML parse and whitespace checks

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