fix(release): skip unrebased PRs in trusted version preparation

[przeprogramowani]

Cause

Hosted Prepare version (#47) failed after #48 merged. That job is version preparation, not npm publish and not Toolkit. prepare-version.yml on master push enumerates every open PR. PR #47 (and #2) still have base.sha at pre-#48 master and do not contain current master, so validatePullRequest / merge-base --is-ancestor reject, and the entrypoint hid that as Trusted version preparation rejected. Same-head CI of #48 succeeded. npm remains 1.22.0; 1.22.1 is unpublished on master.

This is the same class as D56 (stale open PR vs advanced master). A classified non-zero exit would stay persistently red on every later master push.

Change

• Typed BranchUpdateRequiredError for stale REST base and ancestry exit 1.
• reconcileVersionEvent logs it, writes no Git objects and no preparation record, and continues.
• Invalid baseline, missing objects, and identity/fork failures still fail the job.
• Unexpected errors now print the real message.

PR #47 QualityLoop is untouched. No publish/tag/release/Toolkit mutation.

Toolkit

Automatic wake-coordinator on every CLI master push is not required for this stage or for the proven direct publish-npm.yml path. Removing it needs GitHub workflow scope (this token cannot update .github/workflows/ci.yml). Dispatch-only coordinated receipt is kept.

Local proof

Isolated WT from 95fc5f43948e06a4206cf53a812fd493a5619da3. Node 22.14.0, bun 1.3.8, isolated npm 11.12.1. Live SHA replay: first guard is now BranchUpdateRequiredError, 0 writers, reconcile returns null. bun test tests/*.test.ts 795 pass; typecheck; lint 0 errors; validate:cli-skills; actionlint on changed workflows; both builds; 31 smoke.

Not in this PR

Publication of unpublished 1.22.1, merge of #47, Toolkit source, coordinator dispatch.