👷 ci: pick the newest Xcode the runner has

Every macOS job hardcoded /Applications/Xcode_26.app, and the macos-26
image does not ship that name, so all four failed before running a single
check.

Scripts/select-xcode.sh takes the highest-sorting Xcode in /Applications
and refuses anything below 26, which survives the point releases the image
rotates through while still failing loudly if the SDK regresses.

Claude-Session: https://claude.ai/code/session_01CGckDFXvufWVmRH4uyE4z8

Author: gaborbernat

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
           persist-credentials: false
       - uses: jdx/mise-action@c37c93293d6b742fc901e1406b8f764f6fb19dac # v2.4.4
       - name: Select Xcode
-        run: sudo xcode-select -s /Applications/Xcode_26.app/Contents/Developer
+        run: Scripts/select-xcode.sh
       - name: Run every hook
         run: just lint
 
@@ -36,7 +36,7 @@ jobs:
           persist-credentials: false
       - uses: jdx/mise-action@c37c93293d6b742fc901e1406b8f764f6fb19dac # v2.4.4
       - name: Select Xcode
-        run: sudo xcode-select -s /Applications/Xcode_26.app/Contents/Developer && swift --version
+        run: Scripts/select-xcode.sh
       - name: Cache SwiftPM
         uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
         with:
@@ -63,7 +63,7 @@ jobs:
           persist-credentials: false
       - uses: jdx/mise-action@c37c93293d6b742fc901e1406b8f764f6fb19dac # v2.4.4
       - name: Select Xcode
-        run: sudo xcode-select -s /Applications/Xcode_26.app/Contents/Developer
+        run: Scripts/select-xcode.sh
       - name: Generate project
         run: just xcode
       - name: Build

.github/workflows/release.yml

@@ -84,7 +84,7 @@ jobs:
           ref: ${{ env.TAG }}
           persist-credentials: false
       - name: Select Xcode
-        run: sudo xcode-select -s /Applications/Xcode_26.app/Contents/Developer
+        run: Scripts/select-xcode.sh
       - name: Install tools
         run: brew install xcodegen
       - name: Stamp version
@@ -198,7 +198,7 @@ jobs:
           ref: ${{ env.TAG }}
           persist-credentials: false
       - name: Select Xcode
-        run: sudo xcode-select -s /Applications/Xcode_26.app/Contents/Developer
+        run: Scripts/select-xcode.sh
       - name: Install tools
         run: brew install xcodegen
       - name: Stamp version

Scripts/select-xcode.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Runner images name their Xcodes differently between generations (Xcode_26.app, Xcode_26.0.1.app), so pick the newest
+# one installed rather than a fixed path, and refuse anything older than the macOS 26 SDK the app is built against.
+newest="$(find /Applications -maxdepth 1 -name 'Xcode*.app' | sort -V | tail -1)"
+if [ -z "$newest" ]; then
+  echo "No Xcode in /Applications; the package builds with swift alone, the app bundle needs Xcode" >&2
+  exit 1
+fi
+sudo xcode-select -s "$newest/Contents/Developer"
+
+version="$(xcodebuild -version | head -1 | cut -d' ' -f2)"
+if [ "${version%%.*}" -lt 26 ]; then
+  echo "Xcode ${version} is too old, the app needs the macOS 26 SDK" >&2
+  exit 1
+fi
+xcodebuild -version
+swift --version