Fix keychain reuse in release workflow

.github/workflows/release.yml

@@ -69,6 +69,7 @@ jobs:
           fi
           KEYCHAIN_PASSWORD="$(uuidgen)"
           echo "$APPLE_CERTIFICATE_BASE64" | base64 --decode > /tmp/cert.p12
+          security delete-keychain build.keychain >/dev/null 2>&1 || true
           security create-keychain -p "$KEYCHAIN_PASSWORD" build.keychain
           security set-keychain-settings -lut 21600 build.keychain
           security unlock-keychain -p "$KEYCHAIN_PASSWORD" build.keychain
@@ -114,3 +115,9 @@ jobs:
         with:
           files: GhosttyTabs-macos.zip
           generate_release_notes: true
+
+      - name: Cleanup keychain
+        if: always()
+        run: |
+          security delete-keychain build.keychain >/dev/null 2>&1 || true
+          rm -f /tmp/cert.p12