fix(cli): clean up /diff feature review issues

- Remove invalid `commandType` field from diffCommand (SlashCommand has
  no such property; caused a TS build failure).
- Drop duplicate `NumstatResult` interface in gitDiff.ts — it is
  structurally identical to `GitDiffResult`.
- Register the 9 missing `/diff` i18n strings in en.js / zh.js so the
  command is translatable (previously only `Configuration not available.`
  had entries).

packages/cli/src/i18n/locales/en.js

@@ -153,6 +153,22 @@ export default {
     'Configure authentication information for login',
   'Copy the last result or code snippet to clipboard':
     'Copy the last result or code snippet to clipboard',
+  'Show working-tree change stats versus HEAD':
+    'Show working-tree change stats versus HEAD',
+  'Could not determine current working directory.':
+    'Could not determine current working directory.',
+  'Failed to compute git diff stats': 'Failed to compute git diff stats',
+  'No diff available. Either this is not a git repository, HEAD is missing, or a merge/rebase/cherry-pick/revert is in progress.':
+    'No diff available. Either this is not a git repository, HEAD is missing, or a merge/rebase/cherry-pick/revert is in progress.',
+  'Clean working tree — no changes against HEAD.':
+    'Clean working tree — no changes against HEAD.',
+  '{{count}} file changed, +{{added}} / -{{removed}}':
+    '{{count}} file changed, +{{added}} / -{{removed}}',
+  '{{count}} files changed, +{{added}} / -{{removed}}':
+    '{{count}} files changed, +{{added}} / -{{removed}}',
+  '…and {{hidden}} more (showing first {{shown}})':
+    '…and {{hidden}} more (showing first {{shown}})',
+  '(binary)': '(binary)',
 
   // ============================================================================
   // Commands - Agents

packages/cli/src/i18n/locales/zh.js

@@ -149,6 +149,21 @@ export default {
   'Configure authentication information for login': '配置登录认证信息',
   'Copy the last result or code snippet to clipboard':
     '将最后的结果或代码片段复制到剪贴板',
+  'Show working-tree change stats versus HEAD':
+    '显示工作区相对 HEAD 的变更统计',
+  'Could not determine current working directory.': '无法确定当前工作目录。',
+  'Failed to compute git diff stats': '计算 git diff 统计失败',
+  'No diff available. Either this is not a git repository, HEAD is missing, or a merge/rebase/cherry-pick/revert is in progress.':
+    '无可用 diff。可能不是 Git 仓库、HEAD 缺失，或正在执行 merge/rebase/cherry-pick/revert。',
+  'Clean working tree — no changes against HEAD.':
+    '工作区干净 —— 与 HEAD 无差异。',
+  '{{count}} file changed, +{{added}} / -{{removed}}':
+    '{{count}} 个文件变更，+{{added}} / -{{removed}}',
+  '{{count}} files changed, +{{added}} / -{{removed}}':
+    '{{count}} 个文件变更，+{{added}} / -{{removed}}',
+  '…and {{hidden}} more (showing first {{shown}})':
+    '…还有 {{hidden}} 个（仅显示前 {{shown}} 个）',
+  '(binary)': '（二进制）',
 
   // ============================================================================
   // Commands - Agents

packages/cli/src/ui/commands/diffCommand.ts

@@ -140,7 +140,6 @@ export const diffCommand: SlashCommand = {
     return t('Show working-tree change stats versus HEAD');
   },
   kind: CommandKind.BUILT_IN,
-  commandType: 'local',
   supportedModes: ['interactive', 'non_interactive', 'acp'] as const,
   action: diffAction,
 };

packages/core/src/utils/gitDiff.ts

@@ -34,11 +34,6 @@ export interface GitDiffResult {
   perFileStats: Map<string, PerFileStats>;
 }
 
-export interface NumstatResult {
-  stats: GitDiffStats;
-  perFileStats: Map<string, PerFileStats>;
-}
-
 const GIT_TIMEOUT_MS = 5000;
 /** Maximum files retained in per-file results. Matches issue #2997 "50 files" cap. */
 export const MAX_FILES = 50;
@@ -137,7 +132,7 @@ export async function fetchGitDiffHunks(
  * counts. Only the first `MAX_FILES` entries are kept in `perFileStats`, but
  * total stats account for every line.
  */
-export function parseGitNumstat(stdout: string): NumstatResult {
+export function parseGitNumstat(stdout: string): GitDiffResult {
   const lines = stdout.split('\n').filter(Boolean);
   let added = 0;
   let removed = 0;

scripts/unused-keys-only-in-locales.json

@@ -1,5 +1,5 @@
 {
-  "generatedAt": "2026-04-22T15:40:32.318Z",
+  "generatedAt": "2026-04-24T07:26:06.808Z",
   "keys": [
     "  Models: Qwen latest models\n",
     "  qwen auth qwen-oauth     - Authenticate with Qwen OAuth (discontinued)",