test: minimal reusable workflow diagnostic

Adds ci-minimal.yml + ci-minimal-test.yml to diagnose the startup_failure
on the self-test reusable workflow call. To be removed after diagnosis.

Agent-Session: claude/reusable-ci-20260616

.github/workflows/ci-minimal-test.yml

@@ -0,0 +1,12 @@
+name: Minimal Reusable Test
+
+on:
+  push:
+    branches: ['claude/**']
+
+jobs:
+  test:
+    uses: ./.github/workflows/ci-minimal.yml
+    with:
+      test_input: hello
+    secrets: inherit