[P2-11] Add EV load separation

[woopstar]

Scope

• Treat EV load as separate from base house load.
• Avoid training base load forecast on EV spikes.
• Optional EV sensor mapping.

Acceptance criteria

• EV charging does not distort house baseline.
• Planner can account for scheduled EV charging.

Claude Code prompt

Add optional EV load separation to HSEM. Keep EV charging out of base house load forecast and let planner account for scheduled EV charging.