Add reachy_mini mock-deps registry entry (#807)

Lets doc-builder build the pollen-robotics/reachy_mini docs on a bare
runner via light-install + mock_deps, replacing the custom Docker image
the project used before custom_container was dropped.

Mocked deps need system libraries (gi/dbus), are hardware/robot or
optional-extra packages, or are heavy wheels not needed to introspect
docstrings. Validated with a full `doc-builder build --html` (exit 0,
all API pages generated with real signatures/docstrings).

Assisted-by: Claude:claude-opus-4-8

Author: FabienDanieau

src/doc_builder/mock_deps/reachy_mini.txt

@@ -0,0 +1,59 @@
+# Dependencies for building reachy_mini docs without a full install (see mock_imports.py).
+# Bare names are mocked at build time; real:/nodeps: lines are installed for real
+# by `doc-builder light-install` (nodeps: = with --no-deps).
+#
+# Mocked: need system libraries (gi/dbus), are hardware/robot or optional-extra
+# packages, or are heavy wheels not needed to introspect docstrings.
+gi
+dbus
+cv2
+cv2_enumerate_cameras
+mujoco
+rerun
+placo
+placo_utils
+pinocchio
+meshcat
+onnxruntime
+rustypot
+reachy_mini_motor_controller
+reachy_mini_rust_kinematics
+usb
+libusb_package
+soundfile
+sounddevice
+pynput
+gradio_client
+onshape_to_robot
+gpiozero
+lgpio
+nmcli
+pulsectl
+pycaw
+pollen_BMI088_imu_library
+Foundation
+CryptoKit
+real:numpy
+real:scipy
+real:pydantic
+real:fastapi
+real:starlette
+real:uvicorn
+real:aiohttp
+real:websockets
+real:requests
+real:pyyaml
+real:rich
+real:jinja2
+real:huggingface_hub
+real:toml
+real:psutil
+real:questionary
+real:platformdirs
+real:zeroconf
+real:asgiref
+real:semver
+real:cryptography
+real:log-throttling
+real:pyserial
+real:python-multipart