chore(ci): add a workflow to auto-commit docs changes - #59

This is the right approach. #49 showed that postUpgradeTasks isn't an option on the hosted Mend Renovate app (Post-upgrade command 'make docs' has not been added to the allowed list in allowedCommands). A few things to address before this can merge:

1. Renovate detection is still the test stub. github.actor == 'ctreatma' && startsWith(github.head_ref, 'auto') should become something like github.event.pull_request.user.login == 'renovate[bot]' (optionally plus startsWith(github.head_ref, 'renovate/')). github.actor is whoever triggered the run, so it changes when someone else rebases or re-runs the PR.

2. The pushed docs commit won't get any checks. A push made with the default GITHUB_TOKEN doesn't start new workflow runs, so the new head commit has no Validate CLI Docs / lint results. Meanwhile the original commit keeps a failed Validate CLI Docs, because make docs-check fails before the push step runs. If the check is required, the PR stays blocked. Options:

   • push with a GitHub App token (e.g. actions/create-github-app-token) or a PAT, so checks run on the new commit, or
   • on Renovate PRs, make the job succeed once the push succeeds, accepting that the new commit isn't re-validated.

3. Renovate will stop rebasing the branch once the workflow commits to it, the same way it did on #49 ("does not recognize the last commit author and assumes somebody else may have edited the PR"). renovate.json needs the workflow's commit email in gitIgnoredAuthors:

   "gitIgnoredAuthors": ["bot@equinix.noreply.github.com"]

   That could go in this PR.

4. Cleanup:

   • Drop the TEMP commits, the debug step, and the SDK bump and generated docs that were only there to trigger the workflow.
   • Rebase on main. The actions/checkout and actions/setup-go pins here are older than main (checkout v6.1.0, setup-go v7.0.0), so this will conflict.
   • The validate_pr_title.yaml change (removing synchronize) isn't explained. If it's to avoid re-running on the bot push, a note in the description would help. Otherwise it's probably unrelated to this PR.

Once 1–3 are in, the flow described above (Renovate PR → docs rebuilt → lint/docs checks pass → merge → release) should work end to end.