Add Helper CRUD API (input_boolean, counter, timer, etc.)

[jessica-claude]

Description

No typed wrappers exist for HA helper management WebSocket commands. Users who want their apps to programmatically create helpers (e.g., an app that bootstraps its own input_boolean for state tracking) must use raw ws_send_and_wait() with untyped responses.

Helpers created via these WS commands persist across HA restarts (stored in .storage/), making them suitable for apps that self-provision their own state without requiring manual HA setup.

HA WebSocket pattern: Each helper domain registers five commands via DictStorageCollectionWebsocket:

• {domain}/list
• {domain}/create
• {domain}/update
• {domain}/delete
• {domain}/subscribe

Domains to cover: input_boolean, input_number, input_text, input_select, input_datetime, input_button, counter, timer

Use Cases

• App that creates its own input_boolean toggle (e.g., vacation mode, guest mode)
• App that bootstraps a counter for tracking cycles (e.g., air filter replacement)
• App that creates an input_select for user-facing mode selection
• Self-contained apps that don't require users to manually create helpers in HA before installing

Acceptance Criteria

• Add typed methods for list, create, update, delete per helper domain
• Pydantic response models for each helper type
• Convenience method that creates-if-not-exists (idempotent bootstrap)
• Tests cover all new API methods

References

• Identified during MCP gap analysis comparing hassette API surface to HA MCP server capabilities
• Related: Add registry APIs for devices, entities, and areas #285 (registry APIs), Add statistics API support #286 (statistics API)