The const.py comment claimed an empty stored token yields a client that
answers 401 until configured, but NestQuestApiClient raises ValueError
at construction for an empty/whitespace token. Keep the fail-fast guard,
correct the documentation to state the actual contract (default token is
the empty string; options flow validates non-empty; the coordinator must
configure a token first or handle the construction error), and add a
test pinning that client_from_entry with an unconfigured entry raises at
construction instead of building a client that can only 401.
The integration will consume the NestQuest API service (Feature 16) over
HTTP instead of reading the database. This adds the one module that
speaks the panel plane: api_client.py with get_snapshot() and
complete_instance(), a typed NestQuestApiError for transport failures
and non-2xx responses (carrying the HTTP status so 401/404 are
distinguishable), one timeout per request and no retry loops. The HTTP
session is injected, so tests exercise the client against a stub
transport with no network and no aiohttp; the production factory hands
in HA's shared aiohttp session and resolves the base URL and panel
service token off the config entry (options, then entry data, then
defaults). The two new settings are wired into the options flow like
every other section (validation mirrored with the client's constructor
rules); the token is a secret and is never logged or echoed into error
messages. Coordinator wiring is the next task.
overseer