fix(v2): coerce string-encoded numbers/bools in tool arguments

LLMs occasionally return numeric or boolean tool-call fields as JSON
strings (e.g. "3" instead of 3, "true" instead of true), which Go's
strict json.Unmarshal rejects. The strict unmarshal stays as the happy
path; on failure we retry with a coercion pass that walks the target
struct (recursing into nested structs, slices, maps, and pointer fields)
and converts strings to the appropriate kind. Returns the original error
if coercion can't recover.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

v2/tool.go

@@ -104,8 +104,16 @@ func (t Tool) Execute(ctx context.Context, argsJSON string) (string, error) {
 	// Typed tool: unmarshal JSON into the struct, call the function
 	p := reflect.New(t.pTyp)
 	if argsJSON != "" && argsJSON != "{}" {
-		if err := json.Unmarshal([]byte(argsJSON), p.Interface()); err != nil {
-			return "", fmt.Errorf("invalid tool arguments: %w", err)
+		err := json.Unmarshal([]byte(argsJSON), p.Interface())
+		if err != nil {
+			// LLMs sometimes return numeric/boolean fields as JSON strings
+			// (e.g. "3" instead of 3). Retry with type coercion.
+			if coerced, cerr := coerceArgsToType([]byte(argsJSON), t.pTyp); cerr == nil {
+				err = json.Unmarshal(coerced, p.Interface())
+			}
+			if err != nil {
+				return "", fmt.Errorf("invalid tool arguments: %w", err)
+			}
 		}
 	}
 	out := t.fn.Call([]reflect.Value{reflect.ValueOf(ctx), p.Elem()})