feat(coding-agent): isolate SproutClaw namespace from upstream pi

Use piConfig name sproutclaw and configDir .sproutclaw so commands, env vars,
and project config no longer collide with the stock pi install.

Co-authored-by: Cursor <cursoragent@cursor.com>

sproutclaw.bat

@@ -2,8 +2,8 @@
 setlocal
 set "SCRIPT_DIR=%~dp0"
 if "%SCRIPT_DIR:~-1%"=="" set "SCRIPT_DIR=%SCRIPT_DIR:~0,-1%"
-if not defined PI_CODING_AGENT_DIR (
-    set "PI_CODING_AGENT_DIR=%SCRIPT_DIR%.piagent"
+if not defined SPROUTCLAW_CODING_AGENT_DIR (
+    set "SPROUTCLAW_CODING_AGENT_DIR=%SCRIPT_DIR%\.sproutclaw\agent"
 )
 
 if "%~1"=="" goto run