fix(m195): 复审 r1 三项 —— 解压检查点真守卫、presenter 接线测试、取消文案改回真话

P2-1（解压循环检查点没有真守卫）：那条用例原来的断言（status/target/files/bytes/无残留暂存）
在删掉 `extract_overrides` 的检查点后**依然成立**——提交前检查点⑤会替它停一次，于是几 GB 的包
会一直解到结束而测试全绿。改成数 `ImportStage::Extract` 事件：有检查点 = 1 条、删掉 = 3 条
（两面实测）。模块文档同时如实登记"还没有真守卫"的检查点：②③④⑤、全新导入 commit 的取消
分支、phase.rs 远端下载逐条、complete.rs 补全循环的 break。

P2-2（presenter 的真令牌接线零测试）：新增 `pack/tests/cancel.rs`，直接调 `import::run` 并把
传入的 `Arc<AtomicBool>` **预先置 true**，判据只能是盘上事实（目标目录不存在 + profiles.json
零实例）——"没收到 Report"那种判据两条路都成立，`run` 早退条件里的 `cancel.load()` 会把
"没接线"完全遮住。

P2-3（用户可见文案说反了话）：`PackCancelled` 中英双语从「导入会在后台继续跑完 / Import keeps
running in the background…已经写下的文件会留下」改为「导入已取消 —— 后台已停手并回滚：没有留下
半包，也没有覆盖已有文件」；golden 金表同步；`model/tests.rs` 那条把旧文案钉死的用例改成钉新
语义（必须说清停手+回滚，且**禁止**出现 background）；`model.rs` 的 `cancelled` 字段文档与
`dispatch.rs` 的取消注释同族修正。

验证：`cargo test -p unlucky-core -p unlucky-presenter` 1480 passed / 0 failed；
i18n 31 / 0；app-iced packui 28 / 0；三 crate clippy 零 warning。

crates/i18n/src/catalog/content.rs

@@ -179,8 +179,8 @@ macro_rules! content_entries {
             ),
             PackReportRejectedNote => ("not supported by the client", "客户端不支持"),
             PackCancelled => (
-                "Import keeps running in the background — this result is discarded. Files already written stay.",
-                "导入会在后台继续跑完 —— 本次结果作废；已经写下的文件会留下。"
+                "Import cancelled — it stopped and rolled back: nothing was left half-done, no existing files were overwritten.",
+                "导入已取消 —— 后台已停手并回滚：没有留下半包，也没有覆盖已有文件。"
             ),
             PackOverwriteAction => ("Re-import, the pack wins", "以包为准重新导入"),
             PackOverwriteNote => (

crates/i18n/src/catalog/golden/tail2.rs

@@ -29,7 +29,7 @@ pub(super) const ROWS: &[(&str, &str, &str)] = &[
     ("PackReportConflicts", "Conflicts: {count}", "冲突：{count} 个"),
     ("PackReportRejected", "The client does not support these: {count}", "这些组件客户端不支持：{count} 个"),
     ("PackReportRejectedNote", "not supported by the client", "客户端不支持"),
-    ("PackCancelled", "Import keeps running in the background — this result is discarded. Files already written stay.", "导入会在后台继续跑完 —— 本次结果作废；已经写下的文件会留下。"),
+    ("PackCancelled", "Import cancelled — it stopped and rolled back: nothing was left half-done, no existing files were overwritten.", "导入已取消 —— 后台已停手并回滚：没有留下半包，也没有覆盖已有文件。"),
     ("PackOverwriteAction", "Re-import, the pack wins", "以包为准重新导入"),
     ("PackOverwriteNote", "Keeping both (renamed) is not supported yet: for each existing file you pick either “keep” or “overwrite”.", "「两者都留（改名）」暂不支持：每个已存在的文件只能选「保留」或「覆盖」。"),
     ("PackMissingOffline", "offline import", "离线导入"),