fix(release): identify active desktop runtime

[pallyoung]

Summary

• treat the Desktop update coordinator's Product version as the running Runtime source of truth
• keep active.json as a fallback because it may intentionally point at the previous rollback Runtime
• include observed and expected Shell/Runtime versions in acceptance failures
• cover the retained rollback-pointer case

Why

Desktop 0.1.6 successfully installed and relaunched in release run 33040438514. The running Factory Runtime was 0.5.13, while active.json intentionally retained 0.5.8 as the rollback candidate. Installed acceptance read the rollback pointer first and incorrectly rejected the candidate.

Verification

• pnpm exec vitest run --config scripts/vitest.config.ts --environment node scripts/verify-desktop-installed-update.test.ts scripts/github-workflows.test.ts (40 passed)
• pnpm exec biome check scripts/verify-desktop-installed-update.test.ts scripts/verify-desktop-installed-update.ts (passed)