feat: implement AI-assisted rename prompting feature

- Added data model for AI-assisted renaming including structures for prompts, responses, and policies.
- Created implementation plan detailing the integration of Google Genkit into the CLI for renaming tasks.
- Developed quickstart guide for setting up and using the new AI rename functionality.
- Documented research decisions regarding Genkit orchestration and prompt composition.
- Established tasks for phased implementation, including setup, foundational work, and user stories.
- Implemented contract tests to ensure AI rename policies and ledger metadata are correctly applied.
- Developed integration tests for validating AI rename flows, including preview, apply, and undo functionalities.
- Added tooling to pin Genkit dependency for consistent builds.

tests/integration/ai_policy_validation_test.go

@@ -0,0 +1,84 @@
+package integration
+
+import (
+	"bytes"
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	renamercmd "github.com/rogeecn/renamer/cmd"
+	"github.com/rogeecn/renamer/internal/ai/genkit"
+	"github.com/rogeecn/renamer/internal/ai/prompt"
+)
+
+type violatingWorkflow struct{}
+
+func (violatingWorkflow) Run(ctx context.Context, req genkit.Request) (genkit.Result, error) {
+	return genkit.Result{
+		Response: prompt.RenameResponse{
+			Items: []prompt.RenameItem{
+				{
+					Original: "video.mov",
+					Proposed: "001_clickbait-offer.mov",
+					Sequence: 1,
+				},
+			},
+			Warnings: []string{"model returned promotional phrasing"},
+		},
+	}, nil
+}
+
+func TestAIPolicyValidationFailsWithActionableMessage(t *testing.T) {
+	genkit.OverrideWorkflowFactory(func(ctx context.Context, opts genkit.Options) (genkit.WorkflowRunner, error) {
+		return violatingWorkflow{}, nil
+	})
+	t.Cleanup(genkit.ResetWorkflowFactory)
+
+	rootDir := t.TempDir()
+	createAIPolicyFixture(t, filepath.Join(rootDir, "video.mov"))
+
+	rootCmd := renamercmd.NewRootCommand()
+	var stdout, stderr bytes.Buffer
+	rootCmd.SetOut(&stdout)
+	rootCmd.SetErr(&stderr)
+	rootCmd.SetArgs([]string{
+		"ai",
+		"--path", rootDir,
+		"--dry-run",
+		"--naming-casing", "kebab",
+		"--naming-prefix", "proj",
+		"--banned", "offer",
+	})
+
+	err := rootCmd.Execute()
+	if err == nil {
+		t.Fatalf("expected policy violation error")
+	}
+
+	lines := stderr.String()
+	if !strings.Contains(lines, "Policy violation (prefix)") {
+		t.Fatalf("expected prefix violation message in stderr, got: %s", lines)
+	}
+	if !strings.Contains(lines, "Policy violation (banned)") {
+		t.Fatalf("expected banned token message in stderr, got: %s", lines)
+	}
+	if !strings.Contains(err.Error(), "policy violations") {
+		t.Fatalf("expected error to mention policy violations, got: %v", err)
+	}
+
+	if stdout.Len() != 0 {
+		t.Logf("stdout: %s", stdout.String())
+	}
+}
+
+func createAIPolicyFixture(t *testing.T, path string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatalf("mkdir %s: %v", path, err)
+	}
+	if err := os.WriteFile(path, []byte("demo"), 0o644); err != nil {
+		t.Fatalf("write file %s: %v", path, err)
+	}
+}