fix: update default model from claude-sonnet-4-5 to claude-sonnet-4-6 (#1390)

CLAUDE_MEM_MODEL defaulted to the deprecated claude-sonnet-4-5 across source,
installer, tests, and documentation. Updated all references to claude-sonnet-4-6.

Closes #1390

Co-Authored-By: Claude <noreply@anthropic.com>

src/shared/SettingsDefaultsManager.ts

@@ -71,7 +71,7 @@ export class SettingsDefaultsManager {
    * Default values for all settings
    */
   private static readonly DEFAULTS: SettingsDefaults = {
-    CLAUDE_MEM_MODEL: 'claude-sonnet-4-5',
+    CLAUDE_MEM_MODEL: 'claude-sonnet-4-6',
     CLAUDE_MEM_CONTEXT_OBSERVATIONS: '50',
     CLAUDE_MEM_WORKER_PORT: '37777',
     CLAUDE_MEM_WORKER_HOST: '127.0.0.1',

src/ui/viewer/constants/settings.ts

@@ -3,7 +3,7 @@
  * Shared across UI components and hooks
  */
 export const DEFAULT_SETTINGS = {
-  CLAUDE_MEM_MODEL: 'claude-sonnet-4-5',
+  CLAUDE_MEM_MODEL: 'claude-sonnet-4-6',
   CLAUDE_MEM_CONTEXT_OBSERVATIONS: '50',
   CLAUDE_MEM_WORKER_PORT: '37777',
   CLAUDE_MEM_WORKER_HOST: '127.0.0.1',