test(FN-3607): harden test workflow verification and isolation checks

- Expand test-changed coverage and shard selection assertions for CI workflows
- Improve vitest worker temp-directory utilities and related core/CLI tests
- Refine test isolation guardrails and runtime ignore handling for live .fusion noise
- Update contributing guidance and root test script usage for the verified workflow

Fusion-Task-Id: FN-3607

scripts/check-test-isolation.mjs

@@ -58,22 +58,22 @@ function listProtectedFusionDirs() {
 // is expected to mutate. Tests still must not write to these — the filter only
 // suppresses noise from a live app sharing the same HOME during local dev.
 const RUNTIME_IGNORE_PATTERNS = [
-  /^agent(?:[\/\\]|$)/,
-  /^agents(?:[\/\\]|$)/,
-  /^agent-memory(?:[\/\\]|$)/,
-  /^automations(?:[\/\\]|$)/,
-  /^backups(?:[\/\\]|$)/,
-  /^plugins(?:[\/\\]|$)/,
-  /^cache(?:[\/\\]|$)/,
+  /^agent(?:[/\\]|$)/,
+  /^agents(?:[/\\]|$)/,
+  /^agent-memory(?:[/\\]|$)/,
+  /^automations(?:[/\\]|$)/,
+  /^backups(?:[/\\]|$)/,
+  /^plugins(?:[/\\]|$)/,
+  /^cache(?:[/\\]|$)/,
   /^config\.json$/,
   /^fusion-central\.db(?:-wal|-shm|-journal)?$/,
   /^fusion\.db(?:-wal|-shm|-journal)?(?:\.backup-[\w-]+)?$/,
   /^archive\.db(?:-wal|-shm|-journal)?(?:\.backup-[\w-]+)?$/,
   /^activity-log\.jsonl$/,
   /^settings\.json$/,
-  /^logs(?:[\/\\]|$)/,
-  /^tasks(?:[\/\\]|$)/,
-  /^memory(?:[\/\\]|$)/,
+  /^logs(?:[/\\]|$)/,
+  /^tasks(?:[/\\]|$)/,
+  /^memory(?:[/\\]|$)/,
   /^MEMORY\.md$/,
   /^DREAMS\.md$/,
   /^\d{4}-\d{2}-\d{2}\.md$/,