fix(docs): correct sync-dev-after-release docs to match PR-based flow

[brettdavies]

Summary

PR #28 refactored scripts/sync-dev-after-release.sh from direct-commit-to-dev to PR-based flow (cuts a chore/sync-dev-after-vX.Y.Z branch and opens a PR), but the accompanying documentation in RELEASES.md and RELEASES-RATIONALE.md still describes the old direct-commit shape. Bring both docs in sync with the shipped script.

No script changes; this PR only updates the prose that lagged the script.

What changed in RELEASES.md § "After publish — sync dev with the release"

• Replace "commits the result directly to dev as one signed commit (no PR)" with "cuts a chore/sync-dev-after-vX.Y.Z branch off dev and opens a PR".
• Add a pointer to the rationale section explaining the PR-only norm applies here too.
• Update the idempotency line from "exits 0 with no commit" to "exits 0 without creating a branch or PR" to match the script's actual short-circuit behavior.

What changed in RELEASES-RATIONALE.md § "Why backport main → dev after publish"

• Replace the "lands directly on dev (one signed commit, no PR). This is a deliberate exception to the PR-only norm" paragraph with the current behavior: the backport opens a PR, the PR-only norm applies, the mechanical-diff and idempotency arguments justify reviewer spot-check + squash-merge rather than the prior exception-from-norm framing.
• Same idempotency-line correction as RELEASES.md.

Changelog

Fixed

• RELEASES.md and RELEASES-RATIONALE.md corrected to reflect the PR-based dev-sync flow that scripts/sync-dev-after-release.sh has shipped since PR chore(release): refactor sync-dev-after-release.sh to PR-based flow #28. The previous text claimed the backport lands directly on dev as one signed commit; the script actually cuts a chore/sync-dev-after-vX.Y.Z branch and opens a PR.

Type of Change

• fix: Bug fix (non-breaking change which fixes an issue)

Related Issues/Stories

• Architecture: pairs with the PR-based-flow refactor in PR chore(release): refactor sync-dev-after-release.sh to PR-based flow #28 that introduced the staleness; the prose docs lagged the script change.
• Related PRs: this is a sibling fix to brettdavies/agent-skills PR release: v0.2.0 — agent-native CLI skill bundle public launch #12, which lands the same documentation (RELEASES.md + RELEASES-RATIONALE.md + RELEASES-PREFLIGHT.md triad) into the canonical github-repo-setup skill template with the corrected PR-based wording from day one.

Testing

• Manual testing completed

Test Summary:

• markdownlint-cli2 RELEASES.md RELEASES-RATIONALE.md clean on both files.
• No script changes; runtime behavior is unaffected.

Files Modified

Modified:

• RELEASES.md
• RELEASES-RATIONALE.md

Breaking Changes

• No breaking changes

Deployment Notes

• No special deployment steps required

This is a docs-only fix. After merge to dev, the file changes will sit on dev until the next release/* → main cherry-pick brings them onto main (per RELEASES.md's branching model).

Checklist

• Code follows project conventions and style guidelines
• Commit messages follow Conventional Commits
• Self-review of code completed
• No new warnings or errors introduced
• Changes are backward compatible