docs: align v0.1.1 release status

[tcballard]

What changed

• add the signed and notarized download and Homebrew install paths to the README
• replace pre-release wording with the published v0.1.1 (7) state
• record Developer ID, notarization, stapling, Sparkle, and Homebrew verification as complete
• mark Issue release(macos): ship a Developer ID signed and notarized build #24 complete while keeping the Mac App Store channel deferred under Issue release(app-store): ship a sandboxed Mac App Store build #29
• update the WWDC26 comparison and v0.1.1 release notes to match the shipped trust state

Why

The repository documentation still described v0.1.1 as an unpublished candidate after the notarized release, signed appcast, Homebrew update, and product page had gone live.

Impact

People now get a clear trusted installation path, and the documentation no longer implies that the deferred App Store submission blocks the direct release.

Validation

• git diff --check
• ./script/release_identity.sh --verify 0.1.1
• stale pre-release wording scan across README.md and docs/