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.

specs/008-ai-rename-prompt/plan.md

@@ -0,0 +1,80 @@
+# Implementation Plan: AI-Assisted Rename Prompting
+
+**Branch**: `008-ai-rename-prompt` | **Date**: 2025-11-03 | **Spec**: `specs/008-ai-rename-prompt/spec.md`
+**Input**: Feature specification from `/specs/008-ai-rename-prompt/spec.md`
+
+**Note**: This template is filled in by the `/speckit.plan` command. See `.specify/templates/commands/plan.md` for the execution workflow.
+
+## Summary
+
+Introduce a `renamer ai` command that embeds a Google Genkit (Go SDK) workflow inside the CLI execution path. The command collects scope metadata, calls the Genkit pipeline in-process (defaulting to an OpenAI-compatible model), validates the response for sequential, uniform, sanitized filenames, allows operator edits, and records final mappings in the undo ledger while managing `*_MODEL_AUTH_TOKEN` secrets under `$HOME/.config/.renamer/`.
+
+## Technical Context
+
+**Language/Version**: Go 1.24 (CLI + Google Genkit Go SDK)  
+**Primary Dependencies**: `spf13/cobra`, internal traversal/history/output packages, `github.com/google/genkit/go` (with OpenAI-compatible connectors), OpenAI-compatible HTTP client for fallbacks  
+**Storage**: Local filesystem plus `.renamer` append-only ledger; auth tokens cached under `$HOME/.config/.renamer/`  
+**Testing**: `go test ./...` for CLI logic, `npm test` (Vitest) for Genkit prompt workflows, contract/integration suites under `tests/`  
+**Target Platform**: Cross-platform CLI (macOS, Linux, Windows shells) executing in-process Genkit workflows  
+**Project Type**: Single CLI project with integrated Go Genkit module  
+**Performance Goals**: Generate validated rename plan for up to 1,000 files in ≤ 30 seconds round-trip  
+**Constraints**: Genkit workflow must initialize quickly per invocation; AI requests limited to 2 MB payload; ensure user-provided banned terms removed  
+**Scale/Scope**: Typical batches 1–1,000 files; shared Genkit pipeline available for future AI features
+
+## Constitution Check
+
+- Preview flow continues to render deterministic before/after tables and block apply until confirmed, satisfying Preview-First Safety.
+- Undo path records final mappings plus AI prompt/response metadata in `.renamer`, preserving Persistent Undo Ledger guarantees.
+- AI rename integration becomes a composable rule module (`internal/ai`) that declares inputs (prompt spec), validations, and postconditions while orchestrating the Go Genkit workflow inline, aligning with Composable Rule Engine.
+- Scope handling reuses existing traversal services (`internal/traversal`) so filters (`--path`, `-r`, `-d`, `--extensions`) remain enforced per Scope-Aware Traversal.
+- Cobra wiring (`cmd/ai.go`) follows existing CLI standards with help text, flag validation, tests, meeting Ergonomic CLI Stewardship.
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/008-ai-rename-prompt/
+├── plan.md
+├── research.md
+├── data-model.md
+├── quickstart.md
+├── contracts/
+└── tasks.md
+```
+
+### Source Code (repository root)
+
+```text
+cmd/
+├── ai.go                # Genkit-powered command wiring
+├── root.go
+
+internal/
+├── ai/
+│   ├── prompt/          # Prompt assembly, policy enforcement
+│   ├── genkit/          # Go Genkit workflow definitions and model connectors
+│   └── plan/            # Response validation & editing utilities
+├── history/
+├── output/
+├── traversal/
+└── sequence/
+
+tests/
+├── contract/
+├── integration/
+└── unit/
+```
+
+tests/
+├── contract/
+├── integration/
+└── unit/
+
+**Structure Decision**: Extend existing CLI layout by adding an `internal/ai` package that houses Go Genkit workflows invoked directly from `cmd/ai.go`; existing test directories cover the new command with contract/integration suites.
+
+## Complexity Tracking
+
+| Violation | Why Needed | Simpler Alternative Rejected Because |
+|-----------|------------|--------------------------------------|
+| Direct Go Genkit integration | First-class Go SDK keeps execution inline and satisfies CLI-only requirement | Manual REST integration would lose Genkit workflows (retriers, evaluators) and require bespoke prompt templating |