CI(windows): install Python to explicit TargetDir + log exit code

Per-user install landed somewhere my candidate-path check missed. Force the
install dir (LOCALAPPDATA\Python312) so python.exe is found deterministically.
(Linux/mac/arm64 builds succeeded; they only failed re-uploading to an existing
release -- softprops' asset-delete 404s on Gitea. A fresh release avoids that.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs

.gitea/workflows/release.yml

@@ -18,17 +18,17 @@ jobs:
         run: |
           $ErrorActionPreference = "Stop"
           if (-not (Get-Command python -ErrorAction SilentlyContinue)) {
-            Write-Host "Python not found; installing 3.12 (per-user, no admin needed)..."
+            Write-Host "Python not found; installing 3.12 to a fixed dir (no admin needed)..."
             $url = "https://www.python.org/ftp/python/3.12.7/python-3.12.7-amd64.exe"
             Invoke-WebRequest -Uri $url -OutFile "$env:TEMP\py.exe"
-            Start-Process -Wait -FilePath "$env:TEMP\py.exe" -ArgumentList "/quiet","PrependPath=1","Include_test=0"
-            $base = @(
-              "$env:LOCALAPPDATA\Programs\Python\Python312",
-              "C:\Program Files\Python312",
-              "C:\Python312"
-            ) | Where-Object { Test-Path "$_\python.exe" } | Select-Object -First 1
-            if (-not $base) { throw "Python install did not produce python.exe in a known location" }
-            $env:Path = "$base;$base\Scripts;$env:Path"
+            $dir = "$env:LOCALAPPDATA\Python312"
+            $p = Start-Process -Wait -PassThru -FilePath "$env:TEMP\py.exe" `
+                   -ArgumentList "/quiet","TargetDir=$dir","PrependPath=1","Include_test=0"
+            Write-Host "installer exit code: $($p.ExitCode)"
+            if (-not (Test-Path "$dir\python.exe")) {
+              throw "python.exe not found at $dir after install (exit $($p.ExitCode))"
+            }
+            $env:Path = "$dir;$dir\Scripts;$env:Path"
           }
           python --version
           python -m pip install --upgrade pip