fix: respect CLAUDE_MEM_FOLDER_CLAUDEMD_ENABLED setting

The CLAUDE_MEM_FOLDER_CLAUDEMD_ENABLED setting was documented but never
actually checked in code. The folder CLAUDE.md generation ran
unconditionally whenever files were touched.

Changes:
- Add CLAUDE_MEM_FOLDER_CLAUDEMD_ENABLED to SettingsDefaults interface
- Add default value 'false' to DEFAULTS object
- Check setting in ResponseProcessor before calling updateFolderClaudeMdFiles

Fixes the issue identified in issue-600-documentation-audit-features-not-implemented.md:
"The setting CLAUDE_MEM_FOLDER_CLAUDEMD_ENABLED is never read."

src/shared/SettingsDefaultsManager.ts

@@ -51,6 +51,7 @@ export interface SettingsDefaults {
   // Feature Toggles
   CLAUDE_MEM_CONTEXT_SHOW_LAST_SUMMARY: string;
   CLAUDE_MEM_CONTEXT_SHOW_LAST_MESSAGE: string;
+  CLAUDE_MEM_FOLDER_CLAUDEMD_ENABLED: string;
 }
 
 export class SettingsDefaultsManager {
@@ -96,6 +97,7 @@ export class SettingsDefaultsManager {
     // Feature Toggles
     CLAUDE_MEM_CONTEXT_SHOW_LAST_SUMMARY: 'true',
     CLAUDE_MEM_CONTEXT_SHOW_LAST_MESSAGE: 'false',
+    CLAUDE_MEM_FOLDER_CLAUDEMD_ENABLED: 'false',
   };
 
   /**