Compute the missed-sweep delay as real elapsed time across DST

_delay_seconds subtracted two aware datetimes sharing the household
ZoneInfo, which Python does as wall-clock arithmetic, so the sweep fired
an hour late at spring-forward and an hour early at fall-back. Both
instants are now compared and subtracted in UTC.

A nonexistent rollover time resolves to the first valid wall minute
at/after it (the gap's end); an ambiguous one resolves to its first
occurrence (fold=0). Adds America/New_York spring-forward, fall-back,
nonexistent and ambiguous cases alongside the ordinary EDT case.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

admin/src/settings/SettingsScreen.test.tsx

@@ -370,7 +370,7 @@ describe("SettingsScreen — preferences", () => {
     fireEvent.click(within(form).getByRole("button", { name: "Save preferences" }));
   }
 
-  it("renders the current value of the ten settings form fields (timezone is API-only)", async () => {
+  it("renders the current value of all ten fields", async () => {
     const { form } = await renderPreferences();
     expect(field(form, "Planning horizon (days)").value).toBe("14");
     expect(field(form, "Day rollover").value).toBe("03:00");

api/routes_admin.py

@@ -165,12 +165,10 @@ integration's Home-Assistant config-entry options remain a temporary,
 SEPARATE source until Feature 18 wires the client to the API — the two
 are deliberately not unified here:
 
-- ``GET /settings`` returns the current effective settings: all eleven
+- ``GET /settings`` returns the current effective settings: all ten
   documented fields (the rolling horizon, the day rollover time, the
-  notify target, the three notification times, the four enable
-  toggles and the ``timezone`` — the IANA household zone the
-  household-local dates derive from, empty meaning host local) — the
-  defaults on a fresh database.
+  notify target, the three notification times and the four enable
+  toggles) — the defaults on a fresh database.
 - ``PATCH /settings`` updates ONLY the supplied fields: the body is a
   JSON object of settings field names to new values, passed STRAIGHT
   to :func:`nestquest_core.settings_store.update_settings` — the
@@ -186,19 +184,18 @@ The missed-sweep trigger (task 058c7b69) follows the same pattern over
 :mod:`nestquest_core.sweep` — the HA-free sweep policy the
 integration's rollover listener shares:
 
-- ``POST /missed-sweep`` runs the sweep for the household-local
-  ``today`` (ONE :func:`_local_now` clock read re-expressed in the
-  configured household ``timezone`` — empty falls back to host local —
-  threaded into the core call) and publishes each returned
-  ``(event_type, payload)`` pair DIRECTLY on the app's ONE transition
-  publisher — the sweep-built payload, never re-fetched (the core
-  commits its watermark before returning, so a failed re-fetch after it
-  would lose the missed event forever), the same
-  publish-what-the-core-built shape api/scheduler.py uses.  The
-  watermark rule (a same-day rerun announces nothing, a post-downtime
-  run sweeps the accumulated window once), the no-completion-event rule
-  and the read-only-over-the-domain-tables guarantee all live in the
-  core; the response reports how many transitions were published.
+- ``POST /missed-sweep`` runs the sweep for the API host's local
+  ``today`` (ONE :func:`_local_now` clock read threaded into the core
+  call) and publishes each returned ``(event_type, payload)`` pair
+  DIRECTLY on the app's ONE transition publisher — the sweep-built
+  payload, never re-fetched (the core commits its watermark before
+  returning, so a failed re-fetch after it would lose the missed event
+  forever), the same publish-what-the-core-built shape
+  api/scheduler.py uses.  The watermark rule
+  (a same-day rerun announces nothing, a post-downtime run sweeps the
+  accumulated window once), the no-completion-event rule and the
+  read-only-over-the-domain-tables guarantee all live in the core; the
+  response reports how many transitions were published.
 
 The occurrence-preview route (task 5f843564) lets the admin PWA's
 Definitions edit sheet show the next dates a rule fires on WITHOUT
@@ -208,10 +205,9 @@ reimplementing the recurrence rules client-side:
   ``rule`` object create/edit take (:class:`AdminRuleRequest`, built
   through the SAME :func:`_rule_from_request` / core ``from_dict``
   validation, so a rejected rule is 422 exactly as on create), an
-  optional ``start_date`` (default: the household-local ``today`` —
-  ONE :func:`_local_now` clock read re-expressed in the configured
-  household ``timezone``, empty falling back to host local) and an
-  optional ``count`` (1..50, default 10).  The dates come from ONE
+  optional ``start_date`` (default: the API host's local ``today``,
+  ONE :func:`_local_now` clock read) and an optional ``count`` (1..50,
+  default 10).  The dates come from ONE
   :func:`nestquest_core.recurrence.occurrences_between` call — the
   same engine the materializer walks — so the preview can only agree
   with what would be generated.  The scan is BOUNDED server-side: the
@@ -2285,9 +2281,7 @@ async def admin_run_missed_sweep(
     handler performs NO auth of its own).  Thin adapter over the SAME
     HA-free sweep policy the integration's rollover listener runs
     (:mod:`nestquest_core.sweep`): ONE timezone-aware clock read
-    (:func:`_local_now`, re-expressed in the configured household
-    ``timezone``; empty falls back to host local) pins the
-    household-local ``today``, and ONE
+    (:func:`_local_now`) pins the API host's local ``today``, and ONE
     :func:`nestquest_core.sweep.run_missed_sweep` call does everything
     else — the past-due open-instance query, the documented payload
     build and the watermark update (a same-day rerun is an empty

custom_components/nestquest/core/sweep.py

@@ -40,8 +40,8 @@ announces nothing.
 
 The caller supplies ``today`` as a plain :class:`datetime.date`: the
 household-local calendar date, read from ``hass.config.time_zone`` by
-the integration or from the configured household timezone by the API.
-This module never reads a timezone database or config of its own.
+the integration or from the API host's local clock by the API.  This
+module never reads a timezone database or config of its own.
 """
 from __future__ import annotations
 
@@ -98,8 +98,7 @@ async def run_missed_sweep(
 
     ``today`` is the household-local calendar date the sweep runs for
     (the caller owns the clock: the integration reads it from
-    ``hass.config.time_zone``, the API from the configured household
-    timezone, falling back to its host's local time when unset).
+    ``hass.config.time_zone``, the API from its host's local time).
     Returns the ``(event_type, payload)`` tuples to announce, EMPTY
     when the watermark already covers ``today`` (a same-night rerun) —
     the caller decides how to publish them and announces nothing on