[Go Migration] Add kinematics:none support for LED test

[AndySze]

Problem

The led.test fails because Go doesn't support kinematics: none configuration, which is used in tests that don't require motion (like LED-only tests).

Config snippet:

[printer]
kinematics: none

Error:
Go runtime doesn't recognize none as a valid kinematics type and fails during config parsing.

Root Cause

The Go kinematics loader (go/pkg/hosth4/kinematics.go) only supports:

• cartesian
• corexy
• corexz
• delta
• deltesian
• polar
• rotary_delta
• hybrid_corexy
• hybrid_corexz
• winch
• generic_cartesian

It doesn't have a "none" kinematics type for non-motion configurations.

Proposed Fix

Add a none kinematics type that:

1. Has no axes
2. Has no steppers
3. Passes all check_move() calls (or rejects them if motion is attempted)
4. Returns empty position for calc_position()

Files:

• go/pkg/hosth4/kinematics.go - Add noneKinematics struct
• go/pkg/hosth4/runtime.go - Handle kinematics: none in config loading

Affected Tests

• led.test
• manual_stepper.test (may also need this)
• Any test with kinematics: none config

Verification

./scripts/go_migration_golden.py compare --only led --mode strict
./scripts/go_migration_golden.py compare --only manual_stepper --mode strict

Parent Issue

Part of #1