Fix release workflow gaps blocking first macOS beta

- Appcast publish: fetch gh-pages into a local branch before creating
  the worktree. actions/checkout's narrow refspec meant the branch was
  checked out detached, so `git push origin gh-pages` failed with
  "src refspec gh-pages does not match any" on a fresh runner.
- Gate the AltStore source update on an iOS build being part of the
  release; a mac/tvOS-only release has no IPA and would publish a
  broken entry.
- Pass the release tag to update-altstore explicitly (gh's "latest
  release" excludes prereleases), parse the build number correctly for
  beta tags (2.0.0-beta.263 -> 263, not beta.263), use the real
  Yattee-<version>-iOS.ipa asset name, and fail instead of writing a
  size-0 entry with a dead URL when the IPA asset is missing.

.github/workflows/update-altstore.yml

@@ -1,7 +1,16 @@
 name: Update AltStore source
 on:
   workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Release tag to publish (defaults to the latest release)'
+        type: string
+        required: false
   workflow_call:
+    inputs:
+      tag:
+        type: string
+        required: false
 
 jobs:
   update_altstore:
@@ -13,18 +22,29 @@ jobs:
       - uses: actions/checkout@v4
         with:
           ref: main
-      - name: Get version info from latest release
+      - name: Get version info from release
         run: |
-          TAG=$(gh release view --json tagName --jq '.tagName')
+          TAG="${{ inputs.tag }}"
+          if [ -z "$TAG" ]; then
+            TAG=$(gh release view --json tagName --jq '.tagName')
+          fi
+          # Tags are <version>-<build> (stable) or <version>-beta.<build> (beta),
+          # e.g. 2.0.0-263 or 2.0.0-beta.263.
           echo "TAG=${TAG}" >> $GITHUB_ENV
-          echo "VERSION_NUMBER=${TAG%-*}" >> $GITHUB_ENV
-          echo "BUILD_NUMBER=${TAG##*-}" >> $GITHUB_ENV
+          echo "VERSION_NUMBER=${TAG%%-*}" >> $GITHUB_ENV
+          echo "BUILD_NUMBER=${TAG##*[-.]}" >> $GITHUB_ENV
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Get IPA size from release
         run: |
-          SIZE=$(gh release view "${{ env.TAG }}" --json assets --jq '.assets[] | select(.name == "Yattee.ipa") | .size')
-          echo "IPA_SIZE=${SIZE:-0}" >> $GITHUB_ENV
+          IPA_NAME="Yattee-${{ env.VERSION_NUMBER }}-iOS.ipa"
+          SIZE=$(gh release view "${{ env.TAG }}" --json assets --jq ".assets[] | select(.name == \"$IPA_NAME\") | .size")
+          if [ -z "$SIZE" ]; then
+            echo "::error::Release ${{ env.TAG }} has no asset named $IPA_NAME — refusing to publish a broken AltStore entry"
+            exit 1
+          fi
+          echo "IPA_NAME=${IPA_NAME}" >> $GITHUB_ENV
+          echo "IPA_SIZE=${SIZE}" >> $GITHUB_ENV
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Update altstore-source.json
@@ -33,7 +53,7 @@ jobs:
           jq --arg version "${{ env.VERSION_NUMBER }}" \
              --arg build "${{ env.BUILD_NUMBER }}" \
              --arg date "$DATE" \
-             --arg url "https://github.com/yattee/yattee/releases/download/${{ env.TAG }}/Yattee.ipa" \
+             --arg url "https://github.com/yattee/yattee/releases/download/${{ env.TAG }}/${{ env.IPA_NAME }}" \
              --argjson size "${{ env.IPA_SIZE }}" \
              '.apps[0].versions = [{
                version: $version,