Address #130 review: one toolCaller helper for the tool tests

The call/mustCall closures were copied between TestRecordKeepingTools and
TestCatalogAndGardenTools; both now use a file-level toolCaller. The other
notes are left as they are: the 'nothing to change' guard enumerates the
args on purpose (it is the tool's own contract, next to the struct it
checks), and wrapping a sentinel with %w is how every readable refusal in
this package is built.

Co-Authored-By: Claude Fable 5 <[email protected]>

internal/agent/tools_test.go

@@ -123,6 +123,34 @@ func TestToolboxScenario(t *testing.T) {
 	}
 }
 
+// toolCaller returns the two ways a test drives a toolbox: call executes a
+// tool with JSON-encoded args and hands back the raw result (for asserting on
+// refusals), and mustCall fails the test on a tool error and decodes the
+// result into `into` when one is given.
+func toolCaller(t *testing.T, ctx context.Context, box *llm.Toolbox) (
+	call func(name string, args any) llm.ToolResult,
+	mustCall func(name string, args any, into any),
+) {
+	t.Helper()
+	call = func(name string, args any) llm.ToolResult {
+		t.Helper()
+		return box.Execute(ctx, llm.ToolCall{ID: "1", Name: name, Arguments: mustJSON(t, args)})
+	}
+	mustCall = func(name string, args any, into any) {
+		t.Helper()
+		res := call(name, args)
+		if res.IsError {
+			t.Fatalf("%s: %s", name, res.Content)
+		}
+		if into != nil {
+			if err := json.Unmarshal([]byte(res.Content), into); err != nil {
+				t.Fatalf("decode %s: %v (%s)", name, err, res.Content)
+			}
+		}
+	}
+	return call, mustCall
+}
+
 func mustJSON(t *testing.T, v any) json.RawMessage {
 	t.Helper()
 	b, err := json.Marshal(v)
@@ -750,22 +778,7 @@ func TestRecordKeepingTools(t *testing.T) {
 	svc, owner := newAgentTestService(t)
 	box := NewToolbox(svc, owner, "2026-08-23")
 
-	call := func(name string, args any) llm.ToolResult {
+	call, mustCall := toolCaller(t, ctx, box)
-		t.Helper()
-		return box.Execute(ctx, llm.ToolCall{ID: "1", Name: name, Arguments: mustJSON(t, args)})
-	}
-	mustCall := func(name string, args any, into any) {
-		t.Helper()
-		res := call(name, args)
-		if res.IsError {
-			t.Fatalf("%s: %s", name, res.Content)
-		}
-		if into != nil {
-			if err := json.Unmarshal([]byte(res.Content), into); err != nil {
-				t.Fatalf("decode %s: %v (%s)", name, err, res.Content)
-			}
-		}
-	}
 
 	g, err := svc.CreateGarden(ctx, owner, service.GardenInput{Name: "Home", WidthCM: 1200, HeightCM: 800, Notes: "Zone 6a."})
 	if err != nil {
@@ -940,22 +953,7 @@ func TestCatalogAndGardenTools(t *testing.T) {
 	svc, owner := newAgentTestService(t)
 	box := NewToolbox(svc, owner, "2026-08-23")
 
-	call := func(name string, args any) llm.ToolResult {
+	call, mustCall := toolCaller(t, ctx, box)
-		t.Helper()
-		return box.Execute(ctx, llm.ToolCall{ID: "1", Name: name, Arguments: mustJSON(t, args)})
-	}
-	mustCall := func(name string, args any, into any) {
-		t.Helper()
-		res := call(name, args)
-		if res.IsError {
-			t.Fatalf("%s: %s", name, res.Content)
-		}
-		if into != nil {
-			if err := json.Unmarshal([]byte(res.Content), into); err != nil {
-				t.Fatalf("decode %s: %v (%s)", name, err, res.Content)
-			}
-		}
-	}
 
 	// --- create_garden: defaults, then an imperial one with notes.
 	var g domain.Garden