fix: normalize absent installer paths without losing directory identity

apps/desktop/src-tauri/nsis/installer.nsi

@@ -152,12 +152,15 @@ Function CXCanonicalDirectory
     Push "安装目录必须是完整路径。 / An absolute installation path is required."
     Call CXFail
   ${EndIf}
-  ClearErrors
-  GetFullPathName $CXPathFull "$CXPathInput"
-  ${If} ${Errors}
+  ; Unlike NSIS GetFullPathName, Win32's API does not require the final path
+  ; component to exist. Never turn a failed/empty result into the drive root.
+  System::Call 'kernel32::GetFullPathNameW(w "$CXPathInput",i ${NSIS_MAX_STRLEN},w .r0,p 0)i.r1'
+  ${If} $1 = 0
+  ${OrIf} $1 >= ${NSIS_MAX_STRLEN}
     Push "无法读取安装目录。 / Cannot resolve the installation directory."
     Call CXFail
   ${EndIf}
+  StrCpy $CXPathFull $0
   StrLen $0 $CXPathFull
   StrCpy $1 $CXPathFull 1 -1
   ${If} $0 > 3
@@ -224,7 +227,13 @@ Function CXRememberLegacyDirectory
     Push "旧版安装目录不是有效的完整路径，已停止迁移。 / The legacy installation path is not absolute."
     Call CXFail
   ${EndIf}
-  GetFullPathName $CXLegacyDirectory "$0"
+  System::Call 'kernel32::GetFullPathNameW(w r0,i ${NSIS_MAX_STRLEN},w .r2,p 0)i.r1'
+  ${If} $1 = 0
+  ${OrIf} $1 >= ${NSIS_MAX_STRLEN}
+    Push "无法规范化旧版安装目录。 / Cannot normalize the legacy installation directory."
+    Call CXFail
+  ${EndIf}
+  StrCpy $CXLegacyDirectory $2
   StrCpy $0 $CXLegacyDirectory 1 -1
   ${If} $0 != "\"
     StrCpy $CXLegacyDirectory "$CXLegacyDirectory\"
@@ -252,7 +261,13 @@ Function CXValidateDestination
   ${If} $0 == ""
     Return
   ${EndIf}
-  GetFullPathName $CXDestinationFull "$INSTDIR"
+  System::Call 'kernel32::GetFullPathNameW(w "$INSTDIR",i ${NSIS_MAX_STRLEN},w .r0,p 0)i.r1'
+  ${If} $1 = 0
+  ${OrIf} $1 >= ${NSIS_MAX_STRLEN}
+    Push "无法规范化新版本安装目录。 / Cannot normalize the installation destination."
+    Call CXFail
+  ${EndIf}
+  StrCpy $CXDestinationFull $0
   StrCpy $0 $CXDestinationFull 1 -1
   ${If} $0 != "\"
     StrCpy $CXDestinationFull "$CXDestinationFull\"

scripts/windows-install-smoke.ps1

@@ -61,6 +61,19 @@ function Assert-Installed {
     }
   }
 }
+function Reset-FixtureInstallLocation {
+  # Tauri intentionally preserves this install-location value when keeping
+  # user data. The old MSI's AppSearch overrides command-line INSTALLDIR with
+  # it. Remove only values produced by the previous synthetic install so this
+  # fixture accurately represents a legacy default Program Files installation.
+  $key = [Microsoft.Win32.Registry]::CurrentUser.OpenSubKey('Software\yynxxxxx\Codex-X', $true)
+  if ($null -ne $key) {
+    try {
+      $key.DeleteValue('', $false)
+      $key.DeleteValue('InstallDir', $false)
+    } finally { $key.Dispose() }
+  }
+}
 function Remove-TestNsis {
   # _?= avoids NSIS's detached temporary uninstaller process so WaitForExit
   # actually covers registry/files removal. This is NSIS's documented syntax.
@@ -84,6 +97,7 @@ try {
   Invoke-Installer $Installer '/S /UPDATE'
   Assert-Installed
   Remove-TestNsis
+  Reset-FixtureInstallLocation
 
   Write-Host 'Scenario 2: released v0.3.20 machine MSI -> current-user NSIS -> NSIS update.'
   $legacyMsi = Join-Path $Work 'Codex-X-0.3.20.msi'
@@ -97,6 +111,7 @@ try {
   if ($status -ne 0 -or $oldDirectory.Length -eq 0) { throw 'Could not read actual legacy MSI InstallLocation.' }
   $oldPath = $oldDirectory.ToString().TrimEnd('\')
   Write-Host "Actual legacy MSI InstallLocation: $oldPath"
+  if ($oldPath -ne (Join-Path $env:ProgramFiles 'Codex-X')) { throw 'The legacy fixture was not installed to Program Files.' }
   $oldExe = Join-Path $oldPath 'codex-x.exe'
   $oldHash = (Get-FileHash $oldExe).Hash
   # Guard the old directory, a non-existent child, and a junction alias. None
@@ -120,6 +135,7 @@ try {
   Invoke-Installer $Installer '/S /UPDATE'
   Assert-Installed
   Remove-TestNsis
+  Reset-FixtureInstallLocation
 
   Write-Host 'Scenario 3: MSI returns 3010 after removal; separate NSIS install continues without reboot.'
   # A separate fixture copy of the hash-verified released MSI requests a reboot