Timestamps made the idempotency check always false — every run would
rewrite every page. Commit SHA is stable: same source commit produces
identical wikitext, so unchanged pages are correctly skipped.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Gitea blocks vars/secrets prefixed with GITEA_ or GITHUB_.
Also avoids relying on github.server_url which resolves to
github.com rather than the local Gitea instance on this runner.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>