refactor(phase-10): complete type safety enhancement

- Add types/api-responses.ts with ApiResponse<T>, PaginatedResponse<T>
- Add types/errors.ts with comprehensive error type hierarchy
- Replace all any usage (53 → 0, 100% reduction)
- Add RawAPI response interfaces for type-safe mapping
- Update catch blocks to use unknown with type narrowing
- Add getState mock to chatStore tests

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src/store/chatStore.ts

@@ -404,17 +404,18 @@ export const useChatStore = create<ChatState>()(
           m.id === assistantId ? { ...m, runId: result.runId } : m
         ),
       }));
-    } catch (err: any) {
+    } catch (err: unknown) {
       // Gateway not connected — show error in the assistant bubble
+      const errorMessage = err instanceof Error ? err.message : '无法连接 Gateway';
       set((state) => ({
         isStreaming: false,
         messages: state.messages.map((m) =>
           m.id === assistantId
             ? {
                 ...m,
-                content: `⚠️ ${err.message || '无法连接 Gateway'}`,
+                content: `⚠️ ${errorMessage}`,
                 streaming: false,
-                error: err.message,
+                error: errorMessage,
               }
             : m
         ),