test: extend CASES_DIR containment guard to the rest of the suite

#356 introduced safeRmHomeTree/isUnderTestHome to stop tests from deleting
the PRODUCTION ~/codeman-cases tree on platforms where os.homedir() ignores
the $HOME override -- but only applied it to the one file caught doing it
live. CASES_DIR has no CODEMAN_DATA_DIR-style env override at all, so every
other test file's raw rmSync(join(CASES_DIR, ...)) was the same unguarded
pattern, just not yet triggered.

Routes every CASES_DIR delete in these 10 files through safeRmHomeTree:
cli-skill-target, edge-cases, integration-flows, operation-lightspeed,
ralph-integration, routes/case-clone-routes, routes/voice-routes,
session-cleanup, sse-events, sse-subscription-filter.

Also fixes one instance in case-clone-routes.test.ts that mkdirSync'd then
rmSync'd a CASES_DIR path directly with no guard at all -- the exact
clobbering pattern #356 exists to prevent, found by extending the sweep.

Held as a separate commit (and intended as a separate PR once #356 merges)
rather than folding into #356 -- keeps the already-checked skinny fix
reviewable on its own; this is the same bug class applied broadly, not new
functionality.

Verified: all 10 files pass (180 tests), npm run typecheck clean.

test/sse-events.test.ts

@@ -1,6 +1,9 @@
 import { describe, it, expect, beforeAll, afterAll } from 'vitest';
 import { WebServer } from '../src/web/server.js';
 import { EventEmitter } from 'node:events';
+import { safeRmHomeTree } from './mocks/index.js';
+import { homedir } from 'node:os';
+import { join } from 'node:path';
 
 const TEST_PORT = 3107;
 
@@ -295,13 +298,8 @@ describe('SSE Event Types', () => {
       expect(caseCreated).toBeDefined();
       expect((caseCreated?.data as any).name).toBe(caseName);
 
-      // Cleanup
-      const { rmSync } = await import('node:fs');
-      const { join } = await import('node:path');
-      const { homedir } = await import('node:os');
-      try {
-        rmSync(join(homedir(), 'codeman-cases', caseName), { recursive: true });
-      } catch {}
+      // Cleanup (containment-gated)
+      safeRmHomeTree(join(homedir(), 'codeman-cases', caseName));
     });
   });
 });