feat: add update tool definitions

src/tools/definitions/update.rs

@@ -0,0 +1,21 @@
+use serde_json::{json, Value};
+
+pub fn tool_check_update() -> Value {
+    json!({
+        "name": "check_update",
+        "description": "Check if a newer version of mt5-quant is available on GitHub. A background check runs automatically on the first tool call of each session; this tool returns that cached result instantly or fetches it on demand.",
+        "inputSchema": {
+            "type": "object"
+        }
+    })
+}
+
+pub fn tool_update() -> Value {
+    json!({
+        "name": "update",
+        "description": "Download and install the latest mt5-quant binary from GitHub Releases, then replace the current executable in place. Restart the MCP connection after updating to load the new version.",
+        "inputSchema": {
+            "type": "object"
+        }
+    })
+}