ci: xcode-select the chosen Xcode, not just DEVELOPER_DIR

The runner's xcode-select default (Xcode 26.5) disagreed with the
workflow's DEVELOPER_DIR (26.6). Inside xcodebuild-spawned test
processes, the /usr/bin/git shim then loaded Xcode3Core from both
installs and exited 72 — captured verbatim by the probe diagnostic.
Every subprocess-spawning test failure on the macos-26 runners traces
here. Select the same Xcode globally so the shims resolve one install.

Author: arzafran

.github/workflows/ci.yml

@@ -198,6 +198,7 @@ jobs:
           XCODE_DIR="$XCODE_APP/Contents/Developer"
           echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
           export DEVELOPER_DIR="$XCODE_DIR"
+          sudo xcode-select -s "$XCODE_DIR" || true
           xcodebuild -version
 
       - name: Validate Release reload artifact discovery
@@ -370,6 +371,7 @@ jobs:
           XCODE_DIR="$XCODE_APP/Contents/Developer"
           echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
           export DEVELOPER_DIR="$XCODE_DIR"
+          sudo xcode-select -s "$XCODE_DIR" || true
           xcodebuild -version
 
       - name: Cache GhosttyKit.xcframework
@@ -548,6 +550,7 @@ jobs:
           XCODE_DIR="$XCODE_APP/Contents/Developer"
           echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
           export DEVELOPER_DIR="$XCODE_DIR"
+          sudo xcode-select -s "$XCODE_DIR" || true
           xcodebuild -version
           xcrun --sdk macosx --show-sdk-path
 

.github/workflows/release.yml

@@ -184,6 +184,7 @@ jobs:
           XCODE_DIR="$XCODE_APP/Contents/Developer"
           echo "DEVELOPER_DIR=$XCODE_DIR" >> "$GITHUB_ENV"
           export DEVELOPER_DIR="$XCODE_DIR"
+          sudo xcode-select -s "$XCODE_DIR" || true
           xcodebuild -version
           xcrun --sdk macosx --show-sdk-path