fix(i18n): translate the GitHub pull request operations' progress and failure titles (#1169)

The GitHub tool window's long operations passed an untagged banner title and appended " failed" for the error, so the banner stayed English and failures read half translated. withBusy now takes a tx-tagged progress title and its own failure title per operation (checkout, fetch for diff, worktree, apply/commit suggestion, resolve thread).

src/platform/locales/text/zh.json

@@ -5912,5 +5912,14 @@
   "Delete shelved changes “{name}”": "删除搁置的更改“{name}”",
   "Rename shelved changes": "重命名搁置的更改",
   "Passed to the agent process, replacing variables of the same name. Changes apply to new sessions.": "传给智能体进程，覆盖同名变量。对新会话生效。",
-  "Expected NAME=value: {pair}": "应为 NAME=value：{pair}"
+  "Expected NAME=value: {pair}": "应为 NAME=value：{pair}",
+  "Checking out #{number}…": "正在检出 #{number}…",
+  "Couldn't check out #{number}": "无法检出 #{number}",
+  "Fetching #{number}…": "正在获取 #{number}…",
+  "Couldn't fetch #{number}": "无法获取 #{number}",
+  "Creating worktree for #{number}…": "正在为 #{number} 创建工作树…",
+  "Couldn't create the worktree for #{number}": "无法为 #{number} 创建工作树",
+  "Couldn't commit the suggested change": "无法提交建议的更改",
+  "Couldn't apply the suggested change": "无法应用建议的更改",
+  "Couldn't resolve the thread": "无法解决讨论串"
 }