ci: fail hanging tests by name instead of holding the job

Nightly #302 and the PR check for #147 hung in :app-desktop:test for
over an hour, and the log named only the task. Thirteen reruns of the
same commit passed, so the hang is rare and still unidentified.

Every test now gets a two-minute JUnit timeout in a separate thread, so
even an uninterruptible hang fails with the test's name and the stack
where it stood. The test jobs are capped at 20 minutes for a hang
outside any test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/nightly-artifacts.yml

@@ -32,6 +32,9 @@ jobs:
   test:
     name: Test (Java 21, headless)
     runs-on: ubuntu-latest
+    # A healthy run takes about four minutes. The per-test limit in build.gradle.kts names
+    # a hanging test; this cap covers a hang outside any test, such as in Gradle itself.
+    timeout-minutes: 20
 
     steps:
       - name: Checkout

.github/workflows/pr-compile-check.yml

@@ -155,6 +155,9 @@ jobs:
   test:
     name: Test (Java 21, headless)
     runs-on: ubuntu-latest
+    # A healthy run takes about four minutes. The per-test limit in build.gradle.kts names
+    # a hanging test; this cap covers a hang outside any test, such as in Gradle itself.
+    timeout-minutes: 20
 
     steps:
       - name: Checkout

.github/workflows/tagged-release.yml

@@ -24,6 +24,9 @@ jobs:
   test:
     name: Test (Java 21, headless)
     runs-on: ubuntu-latest
+    # A healthy run takes about four minutes. The per-test limit in build.gradle.kts names
+    # a hanging test; this cap covers a hang outside any test, such as in Gradle itself.
+    timeout-minutes: 20
 
     steps:
       - name: Checkout

build.gradle.kts

@@ -141,6 +141,16 @@ subprojects {
             }
             testUserHome.mkdirs()
         }
+        /*
+         * A test that never returns must fail by name instead of holding the job until
+         * GitHub kills it after six hours: Nightly #302 hung in :app-desktop:test for over
+         * an hour, and the log named only the task. The limit is far above the slowest test
+         * (under four seconds). SEPARATE_THREAD also ends a test whose thread ignores
+         * interruption, such as a busy loop or a blocked native call, and the failure's
+         * cause carries that thread's stack, so it shows where the test stood.
+         */
+        systemProperty("junit.jupiter.execution.timeout.default", "2m")
+        systemProperty("junit.jupiter.execution.timeout.thread.mode.default", "SEPARATE_THREAD")
         finalizedBy(checkTestUserHome)
     }