fix(display): schedule windows end at the end time; on-demand ending in off hours blanks at once (#714)

Schedule and dim windows are half-open [start, end): on from the start time, off at exactly the end time, whatever second the check runs. An on-demand session that ends in scheduled-off hours (expiry or stop) clears the once-a-minute schedule gate, so the panel blanks within about a second. Golden: schedule; two test_display_pending_changes.py tests now say end_time 23:00.

Merged with #712 and #713: with all three in, docs/RUN_LOOP_REDESIGN.md's 'may be wrong' list is empty, so that section now records that all six items are fixed and by which PR.

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

docs/ARCHITECTURE.md

@@ -211,7 +211,10 @@ plan for restructuring this loop and lists its golden trace tests.
   to it, rotating between several live games.
 - **Schedule and dim schedule.** `_check_schedule()` reads `schedule`;
   `_check_dim_schedule()` reads `dim_schedule` and
-  `display.hardware.brightness`. Both are re-evaluated once a minute.
+  `display.hardware.brightness`. Both are re-evaluated once a minute, and
+  both windows are half-open: on (or dimmed) from the start time, off at
+  the end time. When an on-demand session ends, the on/off schedule is
+  re-checked at once rather than at the next minute.
 - **Long screens.** While a screen is showing (a dwell, a scroll, a Vegas
   iteration), `_service_pending_changes()` repeats the on-demand, schedule
   and brightness checks every 0.25 s, so a change does not wait for the