Apply settings changes at their save time and retry failed claims

A settings change is now queued with the instant it was saved, and the
loop handles fire times up to that instant under the old rule and later
ones under the new, so a fire time the change made due is not skipped
when the scheduler gets to the change late (SCHED-01).

A failed claim no longer advances the loop past its period: the pass is
repeated every ClaimRetry until the claim succeeds, and periods already
claimed in that pass are skipped by the claim, so each runs once
(SCHED-02).

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

internal/scheduler/scheduler_test.go

@@ -565,6 +565,76 @@ func TestSettingsChangeMovesNextFire(t *testing.T) {
 	wantKeys(t, "the new time", rec.keys(), []string{"2026-10-06", "2026-10-07", "2026-10-09"})
 }
 
+// A change saved at 12:00 moving the 16:30 reminder to 12:01 must fire it
+// even when the scheduler only gets to the change at 12:02, after the new
+// fire time has passed.
+func TestSettingsChangeAppliedLateStillFires(t *testing.T) {
+	e := newEnv(t)
+	var rec recorder
+	// blocker holds the scheduler in a Run at 12:00 on 2026-10-07 while
+	// the settings change and the clock moves on.
+	started := make(chan struct{})
+	release := make(chan struct{})
+	blocker := scheduler.Schedule{
+		Name: scheduler.RotationCheck,
+		Rule: func(household.Settings) scheduler.Rule { return scheduler.Daily("12:00") },
+		Run: func(_ context.Context, p scheduler.Period) error {
+			if p.Key == "2026-10-07" {
+				close(started)
+				<-release
+			}
+			return nil
+		},
+	}
+	r := e.start(at(2026, 10, 7, 11, 0), reminder(&rec), blocker)
+	wantKeys(t, "boot", rec.keys(), []string{"2026-10-06"})
+
+	r.clock.set(at(2026, 10, 7, 12, 0))
+	<-started
+	e.update(household.SettingsPatch{ReminderTime: ptr("12:01")})
+	r.clock.set(at(2026, 10, 7, 12, 2))
+	close(release)
+	r.idle() // the pass the blocker held
+	r.idle() // the pass that applies the change
+	wantKeys(t, "after the late change", rec.keys(), []string{"2026-10-06", "2026-10-07"})
+
+	r.runUntil(at(2026, 10, 7, 23, 0))
+	wantKeys(t, "end of day", rec.keys(), []string{"2026-10-06", "2026-10-07"})
+	wantKeys(t, "claims", e.claimed(scheduler.DayOfReminder), []string{"2026-10-06", "2026-10-07"})
+}
+
+// A claim that fails is retried, not skipped, and the period then runs once.
+func TestClaimFailureIsRetried(t *testing.T) {
+	e := newEnv(t)
+	for _, q := range []string{
+		`CREATE TABLE fail_claims (on_ INTEGER NOT NULL)`,
+		`INSERT INTO fail_claims VALUES (1)`,
+		`CREATE TRIGGER fail_claim BEFORE INSERT ON schedule_runs
+			WHEN (SELECT on_ FROM fail_claims) = 1
+			BEGIN SELECT RAISE(ABORT, 'injected claim failure'); END`,
+	} {
+		if _, err := e.st.Writer.Exec(q); err != nil {
+			t.Fatal(err)
+		}
+	}
+	var rec recorder
+	r := e.start(at(2026, 10, 7, 12, 0), reminder(&rec))
+	wantKeys(t, "boot with failing claims", rec.keys(), nil)
+	wantKeys(t, "claims while failing", e.claimed(scheduler.DayOfReminder), nil)
+	if next, _ := r.clock.nextDeadline(); !next.Equal(at(2026, 10, 7, 12, 0).Add(scheduler.ClaimRetry)) {
+		t.Errorf("next wake %s, want a retry after %s", next, scheduler.ClaimRetry)
+	}
+
+	if _, err := e.st.Writer.Exec(`UPDATE fail_claims SET on_ = 0`); err != nil {
+		t.Fatal(err)
+	}
+	r.runUntil(at(2026, 10, 7, 12, 0).Add(scheduler.ClaimRetry))
+	wantKeys(t, "after the retry", rec.keys(), []string{"2026-10-06"})
+	r.runUntil(at(2026, 10, 7, 23, 0))
+	wantKeys(t, "end of day", rec.keys(), []string{"2026-10-06", "2026-10-07"})
+	wantKeys(t, "claims", e.claimed(scheduler.DayOfReminder), []string{"2026-10-06", "2026-10-07"})
+}
+
 func TestSettingsChangeTimezone(t *testing.T) {
 	e := newEnv(t)
 	var rec recorder