test(ci): isolate CCS-managed env vars from host session

When tests run inside a CCS-managed Claude session, host env vars
(CLAUDE_CONFIG_DIR, CCS_PROFILE_TYPE) leak into subprocess spawns
and fixture setup, causing 9 test failures:

- persist-command-handler: reads real symlinked settings.json instead
  of temp fixture because CLAUDE_CONFIG_DIR overrides scoped CCS_HOME
- websearch-transformer: hook silently exits via shouldSkipHook()
  because CCS_PROFILE_TYPE=account triggers native_account_profile skip
- claudecode-env-stripping: normalizeSharedPluginMetadataPaths receives
  leaked CLAUDE_CONFIG_DIR instead of undefined for default profiles

Fix: clear CCS-managed env vars in beforeEach and neutralize
CCS_PROFILE_TYPE in subprocess env blocks.

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tests/unit/commands/persist-command-handler.test.ts

@@ -73,6 +73,7 @@ function stubProcessExit(): void {
 beforeEach(async () => {
   tempRoot = await fs.promises.mkdtemp(path.join(os.tmpdir(), 'ccs-persist-handler-test-'));
   originalClaudeConfigDir = process.env.CLAUDE_CONFIG_DIR;
+  delete process.env.CLAUDE_CONFIG_DIR;
   originalProcessExit = process.exit;
   originalFsOpen = fs.promises.open;
   originalFsRename = fs.promises.rename;