fix(release): Fix first-release versioning and preview changelogs

[nsdeschenes]

Summary

Fix first-release preparation with auto by upgrading Craft to 2.33.1, and add Craft's changelog preview for pull requests. Craft 2.31.1 turns a missing previous tag into HEAD..HEAD, so it reports no commits despite a complete checkout. The upstream fix landed in Craft #886.

- Craft 2.31.1 (prepare, publish, minimum version)
+ Craft 2.33.1 (prepare, publish, minimum version)
+ Changelog preview reusable workflow and binary pinned to 2.33.1

The preview updates a PR comment on opening, new commits, reopening, title/body edits, and label changes. It uses Craft's documented pull_request_target integration so fork PRs can receive comments; the upstream workflow reads PR metadata and configuration without executing PR code.

Evidence

• Before: The failed Prepare release run reports no commits. A local harness exercising Craft's actual history reader returns 0 commits with 2.31.1.
• After: The same harness returns all 32 commits with 2.33.1. Local auto-version selection chooses 0.1.0; full preparation remains unverified because the dry run timed out.
• Preview workflow YAML parses successfully; its inputs and permissions match the pinned upstream reusable workflow. The preview's GitHub execution can be verified after this workflow reaches main.
• git diff --check and the applicable commit hook passed.

Merge Danger

Door: two-way

The version pins and preview workflow can be reverted.

Blast Radius: automation

Both preparation and publication use the upgraded Craft binary. The preview has permission to write PR comments and commit statuses. No application code changes.