fix: 通知程序改异步后台下载，hook 不再因下载慢阻塞

- exe 缺失时派生脱离 hook 的后台下载进程，立即返回并通过 systemMessage 汇报进度，不受 30s 超时影响
- curl -C - 断点续传，失败保留 .partial 下次接着下
- 原子 mkdir 锁防止多次触发重复下载；进程被硬杀的陈旧锁靠 .partial 闲置自愈
- systemMessage 用 ASCII（中文经 cmd 会被破坏成非法 JSON）

scripts/notify.cmd

@@ -6,40 +6,56 @@ rem ============================================================
 setlocal
 set "BIN=%~dp0..\bin"
 set "EXE=%BIN%\notify.exe"
+set "PART=%BIN%\notify.exe.partial"
 set "LOCK=%BIN%\notify.download.lock"
 
-rem only bootstrap on first run; the common path runs the exe directly (keeps piped stdin intact)
-if not exist "%EXE%" call :bootstrap
+rem hidden self-reinvocation: detached background downloader (see :downloader)
+if "%~1"=="__download" goto downloader
 
-if exist "%EXE%" "%EXE%" %*
-endlocal
-exit /b
-
-:bootstrap
-if not exist "%BIN%" mkdir "%BIN%" 2>nul
-set "TMP=%BIN%\notify.exe.%RANDOM%.tmp"
-rem mkdir is atomic; success = this process downloads, failure = someone else is downloading
-mkdir "%LOCK%" 2>nul
-if errorlevel 1 goto :waitdl
-rem double-check in case it just finished
-if exist "%EXE%" ( rmdir "%LOCK%" 2>nul & exit /b )
-rem download to temp then atomic rename, so no half-written exe is ever seen
-curl -fsSL "%DOWNLOAD_URL%" -o "%TMP%"
-if errorlevel 1 ( del "%TMP%" 2>nul & rmdir "%LOCK%" 2>nul & exit /b )
-move /y "%TMP%" "%EXE%" >nul
-rmdir "%LOCK%" 2>nul
-exit /b
-
-:waitdl
-rem did not get the lock; wait for the exe to appear (up to ~60s)
-set /a _w=0
-:waitloop
-if exist "%EXE%" exit /b
-if %_w% geq 120 (
-    rem timed out; a killed download may have left a stale lock, clear it for next time
-    rmdir "%LOCK%" 2>nul
-    exit /b
+rem common path: exe present -> run directly (keeps piped stdin intact)
+if exist "%EXE%" (
+    "%EXE%" %*
+    endlocal & exit /b
 )
-ping -n 2 127.0.0.1 >nul
-set /a _w+=1
-goto :waitloop
+
+rem ---- exe missing: never block the hook ----
+rem kick off the download once (atomic mkdir lock); a detached worker survives the
+rem hook timeout. then report progress to Claude and return immediately.
+if not exist "%BIN%" mkdir "%BIN%" 2>nul
+
+rem self-heal: if a previous worker was hard-killed (shutdown/crash) it may leave a
+rem stale lock that blocks all retries. reclaim it so -C - can resume the .partial.
+if exist "%LOCK%" call :reclaim
+
+rem atomic lock: only the first hook spawns the worker; others fall through and just
+rem report progress -> no duplicate downloads even when hooks fire concurrently.
+mkdir "%LOCK%" 2>nul && start "" /b "%~f0" __download <nul >nul 2>&1
+
+rem downloaded size so far (from the .partial file), shown as X.X MB
+set "DLBYTES=0"
+if exist "%PART%" for %%A in ("%PART%") do set "DLBYTES=%%~zA"
+set /a DLKB=DLBYTES/1024
+set /a DLMB=DLKB/1024
+set /a DLF=(DLKB*10/1024)%%10
+
+rem exit 0 so Claude parses this JSON; systemMessage is shown to the user, the
+rem notification itself is skipped this time (suppressOutput hides raw stdout)
+echo {"suppressOutput":true,"systemMessage":"[Claude Code Notify] notifier not ready, downloading in background: %DLMB%.%DLF% MB / ~14 MB done. Works automatically once finished; this notification is skipped."}
+endlocal & exit /b 0
+
+:downloader
+rem detached worker: resume-capable download (-C -), atomic install, always free lock.
+rem if curl fails (slow/flaky net), the .partial is kept and the next hook resumes it.
+curl -fsSL -C - "%DOWNLOAD_URL%" -o "%PART%"
+if not errorlevel 1 move /y "%PART%" "%EXE%" >nul 2>&1
+rmdir "%LOCK%" 2>nul
+endlocal & exit /b
+
+:reclaim
+rem no .partial yet => worker died before downloading anything; reclaim immediately
+if not exist "%PART%" ( rmdir "%LOCK%" 2>nul & goto :eof )
+rem .partial idle for >120s => worker is dead (a live curl writes continuously); reclaim
+for /f "delims=" %%T in ('powershell -nop -c "[int]((Get-Date)-(Get-Item '%PART%').LastWriteTime).TotalSeconds" 2^>nul') do set "IDLE=%%T"
+if not defined IDLE goto :eof
+if %IDLE% geq 120 rmdir "%LOCK%" 2>nul
+goto :eof