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>

build.sh

@@ -4,7 +4,7 @@ set -euo pipefail
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PI_CLI_DIST="$SCRIPT_DIR/packages/coding-agent/dist/cli.js"
 
-export PI_CODING_AGENT_DIR="${PI_CODING_AGENT_DIR:-$SCRIPT_DIR/.pi/agent}"
+export SPROUTCLAW_CODING_AGENT_DIR="${SPROUTCLAW_CODING_AGENT_DIR:-$SCRIPT_DIR/.sproutclaw/agent}"
 
 NO_ENV=false
 ARGS=()