feat(home-assistant): split HSEM into 7 per-subsystem devices

[woopstar]

Summary

Splits the single HSEM Home Assistant device into 7 per-subsystem devices: Controller, Battery & Energy, Hourly Consumption Profile, Financial, Forecast, EV Primary, and EV Secondary. Previously every entity (~220+, including the 168 dynamically-created per-hour-block entities) shared one device page, making it impossible to scope automations/dashboards or Areas around a single subsystem.

What changed

• custom_components/hsem/devices.py (new) — HSEMDevice enum (7 members) and get_device_info(entry_id, device) dispatcher. CONTROLLER keeps the original (DOMAIN, entry_id) identifier for backward compatibility; every other device gets (DOMAIN, f"{entry_id}_<device>").
• entity.py — HSEMEntity.device_info now dispatches via a self._hsem_device attribute (defaults to CONTROLLER). Every entity subclass sets it — as a fixed class-level device for single-device entities, or resolved per-instance for entities that come in EV primary/secondary pairs (EV target-SoC number, EV calculated-power/current-limit sensors, OCPP charger sensors keyed by charger_index, and description-driven switches/times).
• utils/sensornames/ev.py / ocpp.py + translations/en.json — EV Secondary and OCPP entity names drop the redundant "Second"/"2" marker (e.g. "OCPP Charger Status" → "Charger Status", rendered as "EV Secondary Charger Status" via _attr_has_entity_name). unique_id and entity_id getters are untouched.
• device_migration.py (new) — one-time entity-registry migration run at the end of async_setup_entry. classify_entity_device(unique_id) offline-classifies each pre-existing registry entry from its frozen unique_id (mirroring the live _hsem_device assignments) and reassigns device_id via entity_registry.async_update_entity. Gated by a hsem_device_migration_version flag stored in entry.data so it runs exactly once per config entry; unique_id is never touched. Also implements (and tests) the new_entity_id rename primitive HA's recorder uses to follow long-term statistics, even though no current entity needs a rename (entity_id getters were kept frozen — only names and device attachment changed).
• Docs — docs/sensors-reference.md (new "Devices" section with the full mapping table), docs/home.md (Devices section + upgrade note), AGENTS.md (Home Assistant Compliance → Device Topology subsection).

Device → entity mapping

Device	Entities
Controller	working mode, degraded mode, read-only, hardware-writes, missing-entities, force-mode, last/next-updated, update-interval, applier-status, plan-explanation, daily-plan-vs-actual, recommendation-interval, force-working-mode selector, extended-attributes/verbose-logging/ML switches
Battery & Energy	battery SoC, effective discharge floor, net consumption, PV curtailment, charge/discharge efficiency numbers, battery schedule 1/2/3 switches + times, dynamic discharge floor switch
Hourly Consumption Profile	all 168 per-hour-block entities
Financial	export income, import cost, net grid balance, savings
Forecast	forecast accuracy, prediction accuracy, solar confidence, Solcast likelihood selector
EV Primary	EV charging/plan sensors, calculated power, current limit, target SoC number, deadline time, EV switches, OCPP charger_index=1
EV Secondary	same set as EV Primary for charger_index=2

Tests

• tests/test_device_split.py (new): devices.py DeviceInfo construction, per-entity device_info dispatch (one test per device including dynamic dispatch cases), classify_entity_device unique_id classification (parametrized across every entity family), and async_migrate_devices (device reassignment, already-correct-device no-op, second-run no-op, entity_id rename primitive, unique_id-never-touched guard).
• tests/custom_sensors/test_ocpp_per_ev.py updated for the new get_ocpp_charger_power_sensor_name() signature/output.

Test & lint results

./scripts/quality.sh lint     # pass
./scripts/quality.sh typing   # pass (0 mypy errors)
./scripts/quality.sh quality  # pass (0 pyright errors; vulture informational-only, pre-existing)
./scripts/quality.sh test     # 3149 passed

Breaking change

⚠️ Existing installs will see entities move to new devices on first startup after upgrading. Dashboards or automations that reference the old single device_id need to be re-pointed to the new devices. unique_ids and entity history/long-term statistics are preserved automatically — the migration never touches unique_id, and no entity_id actually changes in this PR (only display names and device attachment).

Known limitations / out of scope

• Stays within the current hardcoded EV primary/secondary model — generalizing to N arbitrary EVs via config subentries is explicitly out of scope per the issue.

Fixes #875