fix: CI — configure rustup default + PATH for SYSTEM account

Runner runs as SYSTEM which has no rustup default and missing
tool paths. Add GITHUB_PATH entries for Java, cargo, rustup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-release.yml

@@ -50,8 +50,27 @@ jobs:
           Write-Host "Building version: $tag"
 
       # ---------------------------------------------------------------
-      # Verify toolchain
+      # Configure toolchain for SYSTEM account
       # ---------------------------------------------------------------
+      - name: Configure toolchain
+        shell: powershell
+        run: |
+          # Ensure rustup has a default toolchain
+          rustup default stable 2>$null
+
+          # Add tool paths that SYSTEM doesn't have
+          # Java
+          $javaHome = (Get-ChildItem "C:\Program Files\Eclipse Adoptium" -Directory | Select-Object -First 1).FullName
+          if ($javaHome) { echo "$javaHome\bin" >> $env:GITHUB_PATH }
+
+          # Cargo
+          $cargobin = "$env:USERPROFILE\.cargo\bin"
+          if (Test-Path $cargobin) { echo "$cargobin" >> $env:GITHUB_PATH }
+
+          # Rustup
+          $rustupbin = "$env:USERPROFILE\.rustup\toolchains\stable-x86_64-pc-windows-msvc\bin"
+          if (Test-Path $rustupbin) { echo "$rustupbin" >> $env:GITHUB_PATH }
+
       - name: Verify toolchain
         shell: powershell
         run: |