desktop-v0.1.0

fix(desktop): unblock first signed release (#2796)

## Summary
- restore make_latest: false so desktop-v releases do not displace
self-hosted releases/latest
- keep authenticated packaged screenshots as optional release evidence
when the CI-only session fixture exists
- preserve Desktop QA, smoke, signing, notarization, and Gatekeeper
verification as hard release gates
- add release-contract coverage and clarify the fixture in the QA
checklist

## Verification
- Biome focused check: passed
- actionlint desktop workflow check: passed
- secretlint and UI control guard pre-commit hooks: passed
- git diff --check: passed
- local tests/builds not run on this MacBook; GitHub CI is the required
execution gate

## Release intent
After this PR is green and merged, publish desktop-v0.1.0 from the exact
master SHA. The existing website download page discovers desktop-v
releases independently of the self-hosted latest channel.