[codex-action] forward Codex runtime version to Responses

[ftoddywala]

Why

Codex normally includes runtime version metadata on API requests. codex-action routes Codex through a generated local proxy provider, and that path did not preserve the version header. This change forwards the installed Codex version through the proxy provider so upstream services can apply version-aware compatibility behavior.

What changed

• Best-effort read the installed codex --version value when writing the proxy provider config.
• Forward a fully validated version token as the provider's http_headers.version.
• If the version cannot be read or fully parsed, including malformed prerelease/build suffixes, omit the header so the action continues normally.
• Keep the generated action bundle in sync.
• Add focused tests proving valid runtime versions forward and malformed versions omit the header.

Validation

• pnpm run check
• pnpm test

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[ftoddywala]

I have read the CLA Document and I hereby sign the CLA

[ftoddywala]

I have read the CLA Document and I hereby sign the CLA