fix(updater): installer waits for the old cinny.exe to release (#1)

The updater launches the NSIS installer with /UPDATE and then exits the
app, but a WebView2 app takes a moment to die and the template only
sleeps 500 ms after its own kill before copying — so the copy raced the
old process ("Error opening file for writing: cinny.exe"), and Ignore
left the old exe in place.

A NSIS_HOOK_PREINSTALL now, on /UPDATE only, polls until cinny.exe can
really be opened for writing (every 250 ms, up to 15 s), then lets the
template carry on. Checked under Wine with a real running exe: without
the hook the copy fails; with it the installer waits out the remaining
~2.8 s and copies; a manual install (no /UPDATE) doesn't wait; a stuck
process hits the 15 s cap and falls through to the template's own
running-app handling.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src-tauri/nsis/hooks.nsh

@@ -0,0 +1,35 @@
+; Lotus Chat NSIS installer hooks (tauri.conf.json → bundle.windows.nsis.installerHooks).
+
+; cinny-desktop #1 — auto-update hit "Error opening file for writing: cinny.exe".
+; The updater launches this installer with /UPDATE and then exits the running
+; app, but a WebView2 app takes a moment to die; the template only sleeps 500 ms
+; after its own kill before copying files, so the copy raced the old process and
+; Ignore left the old exe in place. On an update, wait until the exe can really
+; be opened for writing (up to 15 s), then let the template carry on as usual.
+!macro NSIS_HOOK_PREINSTALL
+  Push $R7
+  Push $R8
+  Push $R9
+  ClearErrors
+  ${GetOptions} $CMDLINE "/UPDATE" $R7
+  IfErrors lotus_exe_ready
+  IfFileExists "$INSTDIR\${MAINBINARYNAME}.exe" 0 lotus_exe_ready
+  StrCpy $R9 0
+  lotus_exe_probe:
+    ClearErrors
+    FileOpen $R8 "$INSTDIR\${MAINBINARYNAME}.exe" a
+    IfErrors lotus_exe_locked
+    FileClose $R8
+    Goto lotus_exe_ready
+  lotus_exe_locked:
+    IntOp $R9 $R9 + 1
+    ; 60 × 250 ms = 15 s; past that fall through to the template's own
+    ; running-app handling rather than hang the update.
+    IntCmp $R9 60 lotus_exe_ready 0 lotus_exe_ready
+    Sleep 250
+    Goto lotus_exe_probe
+  lotus_exe_ready:
+  Pop $R9
+  Pop $R8
+  Pop $R7
+!macroend

src-tauri/tauri.conf.json

@@ -10,7 +10,8 @@
         "type": "downloadBootstrapper"
       },
       "nsis": {
-        "installMode": "currentUser"
+        "installMode": "currentUser",
+        "installerHooks": "./nsis/hooks.nsh"
       },
       "wix": {
         "bannerPath": "wix/banner.bmp",