Refactor whs.py

[Nomad-01]

Split whs.py apart to make it more agnostic and modular

Modules:

• MAX1238 builder
• SensorReader()
• Valve/draw service
• Run-record writer
• Hardware map
• Clean error handling
• Operator-facing bin/ wrapper

Done when:

• Dry-run works off-Pi where appropriate
• Compile/tests pass
• Hardware assembly occurs in one obvious place
• Business logic is no longer buried in the entrypoint