fix(tui): per-file polish round 12 — locale slice(-0) truncation

truncateLeft (budget 1) and truncateMiddle (maxLength 1-2) computed a
negative slice bound of -0; str.slice(-0) === str.slice(0) returns the
whole string, so callers that clamp the width to 1 via Math.max(1, …)
rendered an ellipsis followed by the full untruncated string, blowing
out the row layout on very narrow terminals. Guard the zero case and add
regression tests.

Author: 3kaiu

MERGE.md

@@ -205,6 +205,7 @@ fork 与上游改了同一处（常见于 TUI 视觉/UX、core 加固逻辑）
 | 逐文件打磨轮7：`component/dialog-model.tsx`（`dialog-{agent,move-session,theme-list,variant,session-delete-failed,session-list,skill,stash,workspace-file-changes,workspace-list}.tsx`+`command-palette.tsx` 已审计） | 中 | 保留 bug 修复：收藏/最近模型选项由可选的 `model.id` 改用可靠的映射键 `item.modelID`（`id?: string` 缺省时 `model.id.includes("-nano")` 抛错、选中项 modelID 变 undefined；并与 providerOptions 分支用键一致）；`dialog-theme-list` `theme.all()` setup 期快照（需订阅 `subscribeThemes` 才能修，`all()` 非响应式且启动后基本不变）择要跳过（上游若已做可取上游版本） |
 | 逐文件打磨轮8：`prompt/{part.ts,frecency.tsx}` + `test/prompt/part.test.ts`（`prompt/{display,history,stash,traits}` + `component/prompt/{history,frecency,stash}` 再导出壳已审计） | 中 | 保留 bug 修复：`expandPastedTextPlaceholders` 的 `String.replace(needle, part.text)` 改函数替换 `() => part.text`（粘贴含 `$&`/`$'`/`$$`/`$n` 的文本经 open-editor/copy 路径被当替换模式解释而损坏，补回归测试）；`frecency` 剪枝 `setStore("data", obj)` 改 `reconcile(obj)`（Solid store 合并语义使被剪路径永不删除，会话内 map 无限增长、每次 update 全量重写 jsonl）（上游若已做可取上游版本） |
 | 逐文件打磨轮9：`context/{kv,data}.tsx`（`context/{permission,prompt,clipboard,editor,path-format,thinking,directory,location}` 已审计） | 低 | 保留 bug 修复：`kv` 读取前先 `Bun.file(file).exists()`，缺文件返回 `{}`（首次启动 `kv.json` 不存在时不再打印误导性的 "Failed to read KV state"，保留真实读/解析错误日志）；`data` 事件驱动的 `catalog/reference/integration.updated` 三处 `void refresh()` 补 `.catch(console.error)`（`throwOnError` 下瞬时失败原为未处理 rejection，与初始加载 allSettled+console.error 一致）；`editor.ts` Zed 轮询代际/`enabled()` 非响应式属自我纠正边角，按审计建议暂缓（上游若已做可取上游版本） |
+| 逐文件打磨轮12：`util/locale.ts` + `test/util/locale.test.ts`（`ui/{dialog,dialog-alert,dialog-confirm,dialog-help,border,activity-verbs}` + `util/{renderer,record,system,signal}` 及轮10 `plugin/*`+`builtins`、轮11 `util/{revert-diff,scroll,selection,transcript,tool-display,model,session,format,path,provider-origin}` 均审计为净） | 中 | 保留 bug 修复：`truncateLeft`/`truncateMiddle` 修 `slice(-0)` 边界（预算=1 或 keepEnd=0 时 `str.slice(-0)===str.slice(0)` 返回整串，`Math.max(1,…)` 钳制的窄终端下 dialog-select/dialog-move-session/workspace-file-changes 会渲染出比原串更长的 `…+整串` 撑爆行），补回归测试（上游若已做可取上游版本） |
 
 ### 其他
 

packages/tui/src/util/locale.ts

@@ -68,7 +68,7 @@ export function truncate(str: string, len: number): string {
 
 export function truncateLeft(str: string, len: number): string {
   if (str.length <= len) return str
-  return "…" + str.slice(-(len - 1))
+  return "…" + (len <= 1 ? "" : str.slice(-(len - 1)))
 }
 
 export function truncateMiddle(str: string, maxLength: number = 35): string {
@@ -78,7 +78,7 @@ export function truncateMiddle(str: string, maxLength: number = 35): string {
   const keepStart = Math.ceil((maxLength - ellipsis.length) / 2)
   const keepEnd = Math.floor((maxLength - ellipsis.length) / 2)
 
-  return str.slice(0, keepStart) + ellipsis + str.slice(-keepEnd)
+  return str.slice(0, keepStart) + ellipsis + (keepEnd === 0 ? "" : str.slice(-keepEnd))
 }
 
 export function pluralize(count: number, singular: string, plural: string): string {

packages/tui/test/util/locale.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, test } from "bun:test"
+import { Locale } from "../../src/util/locale"
+
+describe("Locale truncation", () => {
+  test("truncateLeft respects a width budget of 1", () => {
+    expect(Locale.truncateLeft("abcdef", 1)).toBe("…")
+  })
+
+  test("truncateLeft keeps the tail for larger budgets", () => {
+    expect(Locale.truncateLeft("abcdef", 3)).toBe("…ef")
+  })
+
+  test("truncateLeft returns the string when it already fits", () => {
+    expect(Locale.truncateLeft("ab", 3)).toBe("ab")
+  })
+
+  test("truncateMiddle respects a maxLength of 1 or 2", () => {
+    expect(Locale.truncateMiddle("abcdef", 1)).toBe("…")
+    expect(Locale.truncateMiddle("abcdef", 2)).toBe("a…")
+  })
+
+  test("truncateMiddle keeps both ends for larger budgets", () => {
+    expect(Locale.truncateMiddle("abcdefgh", 5)).toBe("ab…gh")
+  })
+})