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.

internal/history/history.go

@@ -7,6 +7,8 @@ import (
 	"os"
 	"path/filepath"
 	"time"
+
+	"github.com/rogeecn/renamer/internal/ai/prompt"
 )
 
 const ledgerFileName = ".renamer"
@@ -26,6 +28,65 @@ type Entry struct {
 	Metadata   map[string]any `json:"metadata,omitempty"`
 }
 
+const aiMetadataKey = "ai"
+
+// AIMetadata captures AI-specific ledger metadata for rename batches.
+type AIMetadata struct {
+	PromptHash   string                    `json:"promptHash"`
+	ResponseHash string                    `json:"responseHash"`
+	Model        string                    `json:"model"`
+	Policies     prompt.NamingPolicyConfig `json:"policies"`
+	BatchSize    int                       `json:"batchSize"`
+	AppliedAt    time.Time                 `json:"appliedAt"`
+}
+
+// AttachAIMetadata records AI metadata alongside the ledger entry.
+func (e *Entry) AttachAIMetadata(meta AIMetadata) {
+	if e.Metadata == nil {
+		e.Metadata = make(map[string]any)
+	}
+	if meta.AppliedAt.IsZero() {
+		meta.AppliedAt = time.Now().UTC()
+	}
+	e.Metadata[aiMetadataKey] = meta
+}
+
+// AIMetadata extracts AI metadata from the ledger entry if present.
+func (e Entry) AIMetadata() (AIMetadata, bool) {
+	if e.Metadata == nil {
+		return AIMetadata{}, false
+	}
+	raw, ok := e.Metadata[aiMetadataKey]
+	if !ok {
+		return AIMetadata{}, false
+	}
+
+	switch value := raw.(type) {
+	case AIMetadata:
+		return value, true
+	case map[string]any:
+		var meta AIMetadata
+		if err := remarshal(value, &meta); err != nil {
+			return AIMetadata{}, false
+		}
+		return meta, true
+	default:
+		var meta AIMetadata
+		if err := remarshal(value, &meta); err != nil {
+			return AIMetadata{}, false
+		}
+		return meta, true
+	}
+}
+
+func remarshal(value any, target any) error {
+	data, err := json.Marshal(value)
+	if err != nil {
+		return err
+	}
+	return json.Unmarshal(data, target)
+}
+
 // Append writes a new entry to the ledger in newline-delimited JSON format.
 func Append(workingDir string, entry Entry) error {
 	entry.Timestamp = time.Now().UTC()