fix(isolation): add getCcsDir/getCcsHome to more files

Fix test isolation in symlink managers and checkers to prevent tests
from touching user's real ~/.ccs/ and ~/.claude/ directories.

Files fixed:
- src/api/services/profile-writer.ts - use getCcsDir()
- src/management/checks/symlink-check.ts - use functions instead of
  module-level constants
- src/utils/claude-dir-installer.ts - use getCcsDir() for CCS paths
- src/utils/claude-symlink-manager.ts - use getCcsHome()/getCcsDir()

src/api/services/profile-writer.ts

@@ -3,7 +3,6 @@
  * Supports both unified YAML config and legacy JSON config.
  */
 import * as fs from 'fs';
-import * as os from 'os';
 import * as path from 'path';
 import { getCcsDir, getConfigPath, loadConfigSafe } from '../../utils/config-manager';
 import { expandPath } from '../../utils/helpers';
@@ -83,7 +82,7 @@ function createApiProfileUnified(
   apiKey: string,
   models: ModelMapping
 ): void {
-  const ccsDir = path.join(os.homedir(), '.ccs');
+  const ccsDir = getCcsDir();
   const settingsFile = `${name}.settings.json`;
   const settingsPath = path.join(ccsDir, settingsFile);