refactor: migrate all Tauri commands to camelCase parameters

This commit addresses parameter naming inconsistencies caused by Tauri v2's
requirement for camelCase parameter names in IPC commands.

Backend changes (Rust):
- Updated all command parameters from snake_case to camelCase
- Commands affected:
  * provider.rs: providerId (×4), timeoutSecs
  * import_export.rs: filePath (×2), defaultName
  * config.rs: defaultPath
- Added #[allow(non_snake_case)] attributes for camelCase parameters
- Removed unused QueryUsageParams struct

Frontend changes (TypeScript):
- Removed redundant snake_case parameters from all invoke() calls
- Updated API files:
  * usage.ts: removed debug logs, unified to providerId
  * vscode.ts: updated 8 functions (providerId, timeoutSecs, filePath, defaultName)
  * settings.ts: updated 4 functions (defaultPath, filePath, defaultName)
- Ensured all parameters now use camelCase exclusively

Test updates:
- Updated MSW handlers to accept both old and new parameter formats during transition
- Added i18n mock compatibility for tests

Root cause:
The issue stemmed from Tauri v2 strictly requiring camelCase for command
parameters, while the codebase was using snake_case. This caused parameters
like 'provider_id' to not be recognized by the backend, resulting in
"missing providerId parameter" errors.

BREAKING CHANGE: All Tauri command invocations now require camelCase parameters.
Any external tools or scripts calling these commands must be updated accordingly.

Fixes: Usage query always failing with "missing providerId" error
Fixes: Custom endpoint management not receiving provider ID
Fixes: Import/export dialogs not respecting default paths

tests/components/McpFormModal.test.tsx

@@ -19,6 +19,8 @@ vi.mock("react-i18next", () => ({
     t: (key: string, params?: Record<string, unknown>) =>
       params ? `${key}:${JSON.stringify(params)}` : key,
   }),
+  // 提供 initReactI18next 以兼容 i18n 初始化路径
+  initReactI18next: { type: "3rdParty", init: () => {} },
 }));
 
 vi.mock("@/config/mcpPresets", () => ({

tests/msw/handlers.ts

@@ -169,13 +169,21 @@ export const handlers = [
   http.post(`${TAURI_ENDPOINT}/is_portable_mode`, () => success(false)),
 
   http.post(`${TAURI_ENDPOINT}/select_config_directory`, async ({ request }) => {
-    const { default_path } = await withJson<{ default_path?: string }>(request);
-    return success(default_path ? `${default_path}/picked` : "/mock/selected-dir");
+    const { defaultPath, default_path } = await withJson<{
+      defaultPath?: string;
+      default_path?: string;
+    }>(request);
+    const initial = defaultPath ?? default_path;
+    return success(initial ? `${initial}/picked` : "/mock/selected-dir");
   }),
 
   http.post(`${TAURI_ENDPOINT}/pick_directory`, async ({ request }) => {
-    const { default_path } = await withJson<{ default_path?: string }>(request);
-    return success(default_path ? `${default_path}/picked` : "/mock/selected-dir");
+    const { defaultPath, default_path } = await withJson<{
+      defaultPath?: string;
+      default_path?: string;
+    }>(request);
+    const initial = defaultPath ?? default_path;
+    return success(initial ? `${initial}/picked` : "/mock/selected-dir");
   }),
 
   http.post(`${TAURI_ENDPOINT}/open_file_dialog`, () =>