feat: add sql agent (#152)

agents/sql/README.md

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+# SQL
+
+An AI agent that helps you manage a SQL database.
+
+> The tool script uses [usql](https://github.com/xo/usql) to interact with SQL, it supports all mainstream databases. 
+
+![image](https://github.com/user-attachments/assets/28bc1118-5f87-4571-a1c9-6c8cec4636d5)

agents/sql/index.yaml

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+name: Sql
+description: An AI agent that helps you manage a SQL database
+version: 0.1.0
+instructions: |
+  You are an AI agent that manages a SQL database.
+
+  Available tools:
+  {{__tools__}}
+variables:
+  - name: dsn
+    description: The database connection url. e.g. pgsql://user:pass@host:port
+conversation_starters:
+  - What you can do?

agents/sql/tools.sh

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+#!/usr/bin/env bash
+
+set -e
+
+ROOT_DIR="${LLM_ROOT_DIR:-$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)}"
+
+# @meta require-tools usql
+# @env LLM_AGENT_VAR_DSN! The database connection url. e.g. pgsql://user:pass@host:port 
+
+# @cmd Execute a SELECT query
+# @option --query!                  SELECT SQL query to execute
+read_query() {
+    if ! grep -qi '^select' <<<"$argc_query"; then
+        echo "error: only SELECT query is allowed" >&2
+        exit 1
+    fi
+    _run_sql "$argc_query"
+}
+
+# @cmd Execute an SQL query
+# @option --query!                  SQL query to execute
+write_query() {
+    "$ROOT_DIR/utils/guard_operation.sh" "Execute SQL?"
+    _run_sql "$argc_query"
+}
+
+# @cmd List all tables
+list_tables() {
+    _run_sql "\dt+"
+}
+
+# @cmd Get the schema information for a specific table
+# @option --table-name!             Name of the table to describe
+describe_table() {
+    _run_sql "\d $argc_table_name"
+}
+
+_run_sql() {
+    usql "$LLM_AGENT_VAR_DSN" -c "$1" >> "$LLM_OUTPUT"
+}
+
+# See more details at https://github.com/sigoden/argc
+eval "$(argc --argc-eval "$0" "$@")"