Owner's report: «план перезагружается при возврате на вкладку, хотя страница
жива». Diagnosis confirmed: Lovelace re-creates the card element when the
websocket reconnects after a long-backgrounded tab, and the fresh instance ran
the FULL first-open boot — veil + BOOT_MIN_MS + quiescence — reading as a plan
reload. On top of that, _loadFromServer's catch nulled _serverCfg after 8
failed tries, so a slow reconnect could genuinely blank an already-shown plan.
DEV-B703-01 warm re-mount: module-scoped memo (lives with the PAGE, not the
instance) of the settled header height, keyed by viewport size × card config.
A repeat instance adopts the settled geometry in setConfig and skips the veil
entirely — synchronous reveal at the saved zoom (HP-1551); a window resize
between instances changes the key and brings the full protective boot back.
The memo follows the live geometry (updated()'s measure) and is written on
every _bootSettled. Test hook: static _warmBootReset().
DEV-B703-02 stale-while-revalidate: an instance that already renders a valid
config (LS snapshot or a successful load) NEVER clears it on WS failures —
the local-only fallback is reserved for a card that never had a backend. A
self-driven retry (backoff, cap 8 s) keeps revalidating after willUpdate's
8-try budget is spent, and a connection 'ready' hook resets the budget and
quietly re-reads the config the moment the socket is back (the event
subscriptions re-subscribe on their own inside home-assistant-js-websocket).
Smokes: smoke_warm_remount (fails pre-fix: veil + hidden plan on re-mount;
resize invalidation stays cold), smoke_ws_resilience (fails pre-fix:
_serverCfg cleared after 8 tries, no revalidation after recovery); the
preloader smokes now reset the warm memo — they simulate a COLD first open.
