feat: 增强聊天 UI 与终端配置

- 重构消息列表、思考块与工具调用块样式
- ChatContext 支持 agent 分段与 markdown 渲染优化
- 后端增加 PI 命令配置与 Web 终端改进
- 新增 run-backend.sh 启动脚本，忽略 backend/dist 构建产物

run-backend.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SPROUTCLAW_DIR="${SPROUTCLAW_DIR:-$(cd "$SCRIPT_DIR/../sproutclaw" && pwd)}"
+BACKEND_PORT="${BACKEND_PORT:-19133}"
+AGENT_DIR="${SPROUTCLAW_AGENT_DIR:-$SPROUTCLAW_DIR/.sproutclaw/agent}"
+PI_CMD="${SPROUTCLAW_CMD:-node $SPROUTCLAW_DIR/packages/coding-agent/dist/cli.js}"
+
+cd "$SCRIPT_DIR/backend"
+echo "[run-backend] port=$BACKEND_PORT agent-dir=$AGENT_DIR"
+exec go run ./cmd/server \
+  --port "$BACKEND_PORT" \
+  --agent-dir "$AGENT_DIR" \
+  --repo-root "$SPROUTCLAW_DIR" \
+  --pi-cmd "$PI_CMD" \
+  --frontend-dist "$SCRIPT_DIR/frontend/dist" \
+  --data-dir "$SCRIPT_DIR/backend/data"