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/edge-cases.test.ts

@@ -1,8 +1,8 @@
 import { describe, it, expect, beforeAll, afterAll, afterEach } from 'vitest';
 import { WebServer } from '../src/web/server.js';
-import { existsSync, rmSync } from 'node:fs';
 import { join } from 'node:path';
 import { homedir } from 'node:os';
+import { safeRmHomeTree } from './mocks/index.js';
 
 const TEST_PORT = 3110;
 const CASES_DIR = join(homedir(), 'codeman-cases');
@@ -19,13 +19,12 @@ describe('Edge Cases and Error Handling', () => {
   });
 
   afterEach(() => {
-    // Clean up cases created during this test
+    // Clean up cases created during this test. SAFETY: CASES_DIR is
+    // homedir()-derived, which on some platforms ignores the test HOME — the
+    // containment gate refuses to delete anything not under the temp HOME.
     while (createdCases.length > 0) {
       const caseName = createdCases.pop()!;
-      const casePath = join(CASES_DIR, caseName);
-      if (existsSync(casePath)) {
-        rmSync(casePath, { recursive: true, force: true });
-      }
+      safeRmHomeTree(join(CASES_DIR, caseName));
     }
   });
 
@@ -349,15 +348,9 @@ describe('Concurrent Session Handling', () => {
       }
     }
 
-    // Cleanup
-    const { rmSync, existsSync } = await import('node:fs');
-    const { join } = await import('node:path');
-    const { homedir } = await import('node:os');
+    // Cleanup (containment-gated: never touch prod ~/codeman-cases)
     for (const name of createdCases) {
-      const path = join(homedir(), 'codeman-cases', name);
-      if (existsSync(path)) {
-        rmSync(path, { recursive: true, force: true });
-      }
+      safeRmHomeTree(join(homedir(), 'codeman-cases', name));
     }
   });
 });