fix: keep release versioning checks in sync

[MohamedH1998]

What & why

Fix version-dependent CI failures on the release PR (#128) and future version bumps.

• Regenerate the bundled registry during Changesets versioning.
• Check migration review IDs for the current version instead of a fixed count.
• Derive the fixture's packed Nimbus version automatically; keep dependency pins and frozen-install checks intact.

Verified after a real version bump to Nimbus 0.14.0 / CLI 0.7.4 in an isolated worktree: 1,709 tests passed, one skipped; typecheck, API acceptance (including Chromium), and template checks passed. After merge, release automation should refresh #128.

Checklist

• Maintainer-requested work
• Correct tier: release tooling and tests; no starter/template-branch edits
• Changeset and breaking-change declaration not needed: no user-facing changes
• pnpm typecheck, pnpm -r test, and pnpm templates:check pass