refactor: unify env vars (UWF_HOME, OCAS_HOME) + env only in CLI (#37)

Breaking changes:
- UWF_STORAGE_ROOT → UWF_HOME
- WORKFLOW_STORAGE_ROOT removed (no fallback)
- OCAS_DIR → OCAS_HOME (aligned with ocas CLI)

Library functions no longer read process.env:
- util-agent/storage.ts: resolveStorageRoot(override), getGlobalCasDir(override)
- agent-hermes: isResumeDisabled(flag) pure function, CLI reads env
- agent-claude-code: CLI reads CLAUDE_MODEL and passes to agent

Fixes #37

packages/cli/src/__tests__/thread-show-status.test.ts

@@ -305,8 +305,8 @@ describe("thread show status field", () => {
     await setupTestEnv();
     const casDir = join(tmpDir, "cas");
     await mkdir(casDir, { recursive: true });
-    const originalCasDir = process.env.OCAS_DIR;
-    process.env.OCAS_DIR = casDir;
+    const originalCasDir = process.env.OCAS_HOME;
+    process.env.OCAS_HOME = casDir;
 
     try {
       const workflowPath = join(tmpDir, "test-suspend-status.yaml");
@@ -331,9 +331,9 @@ describe("thread show status field", () => {
       expect(result.thread).toBe(threadId);
     } finally {
       if (originalCasDir === undefined) {
-        delete process.env.OCAS_DIR;
+        delete process.env.OCAS_HOME;
       } else {
-        process.env.OCAS_DIR = originalCasDir;
+        process.env.OCAS_HOME = originalCasDir;
       }
       await teardown();
     }