feat(tools): src/lerobot/tools/ — runnable tool registry + SayTool

Ships the runtime side of the OpenAI-style function-calling stack
introduced in PR 1 (catalog in ``meta/info.json["tools"]``) and PR 2
(annotation pipeline writes the catalog after a run). One file per
tool — heavy deps stay isolated.

Layout:

- ``base.py`` — :class:`Tool` Protocol: ``name``, ``schema``,
  ``call(arguments)``. Runtime-checkable so tests can use
  ``isinstance(...)``.
- ``registry.py`` — :data:`TOOL_REGISTRY` (name → class) plus
  ``get_tools(meta, **kwargs)`` that instantiates every entry whose
  ``function.name`` is registered. Tools whose name is unknown are
  silently skipped — the schema still rides through the chat
  template, the model just can't actually invoke that tool at
  inference.
- ``say.py`` — :class:`SayTool` wrapping Kyutai's pocket-tts
  (CPU-only, ~100M params, ~6× real-time on a MacBook Air M4).
  Lazy model load: pocket-tts is imported and the voice state
  computed on first ``call(...)`` (or eagerly via ``preload()``).
  Returns the PCM tensor; optionally writes a ``.wav`` to
  ``output_dir`` for offline inspection.
- ``__init__.py`` — re-exports the public surface.

Optional install:

    pip install lerobot[tools]

The ``[tools]`` extra in ``pyproject.toml`` pulls in ``pocket-tts`` +
``scipy`` (for the wav writer). Adding more tools later means a new
file + a registry entry — no new extras unless the tool brings new
deps.

To add your own tool, follow the three-step guide in
``docs/source/tools.mdx`` (PR 1):

  1. Drop ``src/lerobot/tools/<my_tool>.py`` with a ``Tool``-conforming
     class.
  2. Register the class in ``TOOL_REGISTRY`` (this file).
  3. Pre-populate ``meta/info.json["tools"]`` with the schema (or let
     ``lerobot-annotate`` add it on the next run).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -209,6 +209,14 @@ annotations = [
     "vllm>=0.6.0,<1.0.0; sys_platform == 'linux'",
 ]
 
+# Tool implementations under src/lerobot/tools/. Each tool's dependencies
+# are isolated so adding a new tool doesn't bloat the base install.
+# Currently only `say` (Kyutai pocket-tts; CPU-only, ~100M params).
+tools = [
+    "pocket-tts>=0.1.0,<1.0.0",
+    "scipy>=1.11.0,<2.0.0",  # SayTool.output_dir uses scipy.io.wavfile
+]
+
 # Development
 dev = ["pre-commit>=3.7.0,<5.0.0", "debugpy>=1.8.1,<1.9.0", "lerobot[grpcio-dep]", "grpcio-tools==1.73.1", "mypy>=1.19.1", "ruff>=0.14.1", "lerobot[notebook]"]
 notebook = ["jupyter>=1.0.0,<2.0.0", "ipykernel>=6.0.0,<7.0.0"]