docs: add repository-grounded hardware and firmware guidance

[BotshareAI]

Outcome

Replaces the remaining generic framework pages for the validated mobile-platform hardware and Teensy firmware with project-specific engineering content sourced from the owning repositories.

Hardware coverage

• base vs optional/roadmap architecture
• verified Teensy, motor-driver, encoder, IMU, and power wiring
• wheel-module assembly
• component and drivetrain specification
• BLDC/ZBLD commissioning
• driver fault-code diagnosis

Firmware coverage

• 50 Hz control loop, PID/feedforward, kinematics, odometry, and watchdog behavior
• runtime debug/tuning contract
• pinned linorobot2 overlay build and Teensy flashing
• micro-ROS transport, topics, state machine, IMU behavior, and LED codes
• per-boot encoder-ripple calibration
• transport, flashing, encoder, PID, and powered-debug troubleshooting

Engineering safeguards

• every page identifies its canonical repository file
• experimental status and applicability are explicit
• safety boundaries cover lifted-wheel testing, powered debug, 3.3 V-only encoder supply, battery protection, and physical E-stop limitations
• optional/roadmap hardware is separated from the validated base build
• planned repository scaffolding is not described as implemented capability

Validation

• .venv/bin/mkdocs build --strict
• git diff --check
• no generic placeholder markers remain in these 12 pages