Release v0.5.0

[Smasduq]

Release v0.5.0

This PR prepares the v0.5.0 release.

What's included

• commitor revert — undo commits produced by commitor commit (hard reset for unpushed, git revert for pushed).
• commitor scan --diff-range <RANGE> — analyze a fixed git range instead of the working tree, plus --markdown for PR comments.
• commitor scan --context "<title/description>" — forward a PR's stated intent to the model.
• Post-commit push in commitor commit — offers to push the new branch, auto-detecting the upstream.
• Per-repo session history of commitor commit runs at ~/.commitor/history/<repo-id>.jsonl.
• GitHub Action (./action) that runs commitor scan --diff-range on PRs and posts an updatable Markdown comment.
• commitor commit gains interactive branch selection, base-branch tracking, and an offline mode.
• PR-scale analysis: --diff-range scans now always consult the backend (the local heuristic is advisory only at PR scale), so unrelated changes in a large diff are no longer missed.
• Fixed: release workflow (publish.yml) is now idempotent — re-running a release no longer fails on an already-published crates.io / npm version.

Checklist

• Changelog reviewed
• Version bump verified (Cargo.toml + npm = 0.5.0)
• CI passing

After merging, create the tag on the merge commit:

git tag v0.5.0 <merge-commit-sha>
git push origin v0.5.0

Note: the previous v0.5.0 tag was a phantom (pointed at code still versioned 0.4.0). Delete it before re-tagging this release:

git push origin --delete v0.5.0
git tag v0.5.0 <merge-commit-sha>
git push origin v0.5.0