fix(homebrew): preserve app code signature

[DevVig]

Issue

Launching the Homebrew-installed app could produce macOS's “Microbridge is
damaged and can’t be opened” alert even though the release app was signed,
notarized, and stapled correctly.

Root cause and user impact

The Formula copied Microbridge.app to ~/Applications, then wrote
.microbridge-brew inside the bundle root. That post-signing mutation broke the
sealed resource envelope. codesign and Gatekeeper consequently rejected the
copied app as unsealed contents present in the bundle root.

This affected the Homebrew install path. Direct DMG apps remained valid.

Fix

• Move Homebrew's ownership marker beside the bundle at
  ~/Applications/.Microbridge.app.microbridge-brew.
• Preserve migration support for older installs carrying the legacy in-bundle
  marker; the next service start replaces that owned bundle with a clean copy.
• Teach the app to identify the new sidecar marker so Homebrew installs continue
  routing updates through brew upgrade.
• Make local and final-release Homebrew smoke tests fail unless the installed
  app passes strict code-signing, Gatekeeper, stapler, and Apple distribution
  checks.

Verification

• Reproduced the defect on the old Formula: codesign reported
  unsealed contents present in the bundle root and Gatekeeper rejected it.
• Clean public-asset Homebrew lifecycle with the new marker passed.
• Installed app reported valid on disk, accepted, and
  source=Notarized Developer ID.
• xcrun stapler validate and syspolicy_check distribution passed.
• App launch, service lifecycle, uninstall, and marker cleanup passed.
• make ci passed: 62 Rust tests, 4 Cursor hook tests, 9 UI tests, Clippy,
  formatting, and production UI build.
• Tauri crate check, shell syntax, Formula syntax, and workflow YAML parsing
  passed.

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📥 Commits

Reviewing files that changed from the base of the PR and between d9c9a54 and 061167f.

📒 Files selected for processing (4)

• .github/workflows/finalize-release.yml
• Formula/microbridge.rb
• apps/microbridge-ui/src-tauri/src/lib.rs
• scripts/smoke-formula.sh

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[Copilot]

Pull request overview

This PR fixes Homebrew-installed macOS app signature breakage by moving Homebrew’s ownership marker outside the signed Microbridge.app bundle, preventing post-signing mutations that cause Gatekeeper/codesign rejection.

Changes:

• Updates the Homebrew formula’s service wrapper to write a sidecar marker (~/Applications/.Microbridge.app.microbridge-brew) instead of a file inside the app bundle, while preserving migration support for legacy installs.
• Updates the Tauri app to detect the new sidecar marker (and still recognize the legacy in-bundle marker for migration).
• Strengthens Homebrew smoke checks (script + release workflow) to validate codesign, Gatekeeper assessment, stapling, and distribution policy.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
scripts/smoke-formula.sh	Switches to sidecar marker + adds strict macOS signing/Gatekeeper/stapler/distribution verification in smoke test.
Formula/microbridge.rb	Writes the Homebrew ownership marker beside the app bundle (and supports legacy marker detection to decide ownership).
apps/microbridge-ui/src-tauri/src/lib.rs	Detects sidecar marker (with legacy fallback) to keep update routing consistent for Homebrew installs.
.github/workflows/finalize-release.yml	Adds sidecar marker checks and strict signing/Gatekeeper/stapler/distribution validation in final release verification.

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