fix: fix 7 failing tests (OCAS_DIR → OCAS_HOME + restore workflow destructure)

Root cause: tests used OCAS_DIR env var but store.ts reads OCAS_HOME,
causing tests to hit the global ~/.ocas vars instead of temp dirs.

- store-unified-threads.test.ts: OCAS_DIR → OCAS_HOME (3 tests)
- thread-resume.test.ts: OCAS_DIR → OCAS_HOME (3 tests)
- current-role.test.ts: restore { thread, workflow } destructure
  that was incorrectly removed by biome unsafe fix (1 test)

Result: 745 passed, 0 failed, 1 skipped

Closes #49

packages/cli/src/__tests__/current-role.test.ts

@@ -324,7 +324,7 @@ describe("currentRole field", () => {
     try {
       const wf = join(tmpDir, "test-current-role.yaml");
       await writeFile(wf, SIMPLE_WORKFLOW_YAML, "utf8");
-      const { thread } = await cmdThreadStart(storageRoot, wf, "test", tmpDir);
+      const { thread, workflow } = await cmdThreadStart(storageRoot, wf, "test", tmpDir);
       const tid = thread as ThreadId;
 
       await createMarker(storageRoot, {