refactor(cli): group commands by noun-verb pattern (RFC #54)

Phase 1: workflow subcommand group (add/list/show/rm/history/rollback)
Phase 2: thread subcommand group (run/list/show/rm/fork/ps/kill/live/pause/resume)
Phase 3: cas gc + top-level aliases + deprecation warnings for old flat commands

- Follow existing CAS_SUBCOMMAND_TABLE pattern for workflow and thread groups
- Top-level 'run' and 'live' stay as shortcuts (no deprecation)
- Old flat commands print deprecation warning then delegate
- Update usage string to show grouped format
- Update tests to use new grouped syntax

packages/cli-workflow/__tests__/thread-cli.test.ts

@@ -250,13 +250,16 @@ describe("cli thread commands", () => {
 
   test("cli entrypoint dispatches threads / ps (spawn)", () => {
     const env = { ...process.env, UNCAGED_WORKFLOW_STORAGE_ROOT: storageRoot };
-    const threads = spawnSync(process.execPath, [cliEntryPath, "threads"], {
+    const threads = spawnSync(process.execPath, [cliEntryPath, "thread", "list"], {
       env,
       encoding: "utf8",
     });
     expect(threads.status).toBe(0);
 
-    const ps = spawnSync(process.execPath, [cliEntryPath, "ps"], { env, encoding: "utf8" });
+    const ps = spawnSync(process.execPath, [cliEntryPath, "thread", "ps"], {
+      env,
+      encoding: "utf8",
+    });
     expect(ps.status).toBe(0);
   });