chore(vendor): import pi 0.85.1

Imported as a linear vendor commit so forge rebases do not replay the upstream root tree.

git-subtree-dir: third_party/pi

git-subtree-split: d981de1229ef899957bbe968bc8dcda02a21f477

third_party/pi/pi-test.bat

@@ -0,0 +1,14 @@
+@echo off
+setlocal
+
+set "SCRIPT_DIR=%~dp0"
+set "POWERSHELL_EXE=powershell.exe"
+
+where %POWERSHELL_EXE% >nul 2>nul
+if errorlevel 1 (
+	>&2 echo powershell.exe not found. Install PowerShell or run pi-test.ps1 directly.
+	exit /b 1
+)
+
+%POWERSHELL_EXE% -NoProfile -ExecutionPolicy Bypass -File "%SCRIPT_DIR%pi-test.ps1" %*
+exit /b %ERRORLEVEL%