Add Sparkle-based app updater and release appcast artifacts

[nikuscs]

Integrates Sparkle into the macOS app and adds a new updater view model exposed in the menu bar via a Check for Updates action. Adds SUFeedURL and SUPublicEDKey to the app Info.plist and wires Sparkle as an Xcode package dependency. Updates the release workflow to produce a versioned zip, sign it with Sparkle, generate appcast.xml, and upload zip/appcast alongside the DMG. This enables in-app update checks against GitHub Releases artifacts.

---

[devin-ai-integration]

Devin Review found 1 potential issue.

View 4 additional findings in Devin Review.

[devin-ai-integration]

🔴 Appcast sparkle:version uses marketing version instead of build number, breaking update detection

The appcast.xml sets sparkle:version to the semantic version string (e.g., 1.2.3), but the app's CFBundleVersion is set to a computed build number (e.g., 10203 for version 1.2.3) at .github/workflows/release.yml:135.

Root Cause and Impact

Sparkle compares sparkle:version from the appcast against the running app's CFBundleVersion to determine if an update is available. The workflow computes CFBundleVersion as MAJOR * 10000 + MINOR * 100 + PATCH (e.g., version 1.2.3 → build 10203) at line 135:

BUILD=$((MAJOR * 10000 + MINOR * 100 + PATCH))

But the appcast sets sparkle:version to the raw semantic version string ${VERSION} (e.g., 1.2.3):

<sparkle:version>${VERSION}</sparkle:version>

Sparkle's SUStandardVersionComparator splits version strings by . and compares components. When comparing appcast's 1.2.3 (components: [1, 2, 3]) against the installed app's 10203 (single component: [10203]), the first component comparison is 1 vs 10203 — the installed version always appears newer.

Impact: Sparkle will never offer updates to users because it always thinks the installed version is newer than the version advertised in the appcast. The entire auto-update feature is non-functional.

The fix is to set sparkle:version to the same computed build number used for CFBundleVersion, e.g.:

<sparkle:version>${BUILD}</sparkle:version>

This requires computing the BUILD variable in the "Generate appcast.xml" step or passing it as an output from the version step.

Prompt for agents

In .github/workflows/release.yml, the 'Generate appcast.xml' step at line 273 sets sparkle:version to the semantic version string (VERSION, e.g. '1.2.3'), but it must match CFBundleVersion which is computed as MAJOR*10000 + MINOR*100 + PATCH (e.g. 10203) at line 135.

To fix this:
1. In the 'Get version from tag' step (around line 127), add an output for the build number by adding this line after line 135:
   echo "build=$BUILD" >> $GITHUB_OUTPUT

2. In the 'Generate appcast.xml' step (around line 259), add a BUILD variable:
   BUILD="${{ steps.version.outputs.build }}"

3. Change line 273 from:
   <sparkle:version>${VERSION}</sparkle:version>
   to:
   <sparkle:version>${BUILD}</sparkle:version>

This ensures sparkle:version matches CFBundleVersion so Sparkle can correctly detect when updates are available.

---

Was this helpful? React with 👍 or 👎 to provide feedback.