next iteration on display, still some artifacting issues, and ux with buttons states and updating

TODO.md

@@ -2,20 +2,22 @@
 
 ## Not yet verified on hardware
 
-Flashed and booting clean (icons on, first poll ~8s, no errors), but eyes and
-fingers haven't confirmed:
+Flashed and booting clean (two-phase display init, icons on, first poll ~9s,
+no errors), but eyes and fingers haven't confirmed:
 
-1. Touch actually toggling a light end-to-end. Tiles are now **optimistic**:
-   they flip on tap immediately and hold that state up to 5s until HA
-   confirms (see `light_hold_t` in ui_manager.c). If a tile flips then snaps
-   back 5s later, the command failed — check `ha_client` on serial.
-2. Whether the full-screen invalidate after each poll actually bounds the
-   left-edge artefacts (it repaints them away; it cannot prevent them). If
-   lines still persist for longer than one poll interval, that mechanism is
-   not working and the next lever is pausing only around LVGL's flush.
-3. That the six light tiles are comfortable finger targets at ~125px, and
-   that sliders track the finger without jumping (poll updates skip pressed
-   sliders by design).
+1. Slider feel: press sends one command at the touch position immediately,
+   drag is display-only tracking the finger, lift sends the final level.
+   Poll data never moves a pressed knob.
+2. Trend arrows appear ~5 minutes after boot (indoor big card, outdoor and
+   pressure cells) once the local ring has history. They are local-history
+   based and reset on reboot — that is by design, not a bug.
+3. Artefact lifetime: interactions schedule a one-shot full repaint 600ms
+   after the last touch, and every poll repaints too. Artefacts should now
+   visibly self-clean in under a second after touching, and within a poll
+   otherwise. If they *persist* beyond that, the repaint isn't reaching
+   them; if they merely *recur* during interaction, that is the PSRAM
+   bandwidth ceiling (README) and the honest remaining levers are fewer
+   redraws or 120MHz PSRAM on a newer IDF.
 
 ## Done
 
@@ -95,8 +97,10 @@ hosts the thermostat before building it twice.
 - The `°` glyph exists in LVGL's built-in Montserrat fonts; the `·` separator
   that does not appears only in log strings, never on screen.
 - LVGL recursive-mutex locking is consistent across all UI entry points.
-- Init order in `main.c` is deliberate and load-bearing: WiFi/NVS before
-  `display_init()`, `backlight_init()` before `touch_init()`. Never reorder.
+- Init order in `main.c` is deliberate and load-bearing:
+  `display_alloc()` before WiFi (contiguous bounce buffers from a virgin
+  heap), WiFi/NVS before `display_start()` (flash writes finished before
+  scan-out), `backlight_init()` before `touch_init()`. Never reorder.
 - The bounce buffer is enabled and load-bearing.
 - Board is N16R8 (16MB flash / 8MB octal PSRAM).
 - `touch_get_indev()`, `display_get_panel()` and `lvgl_port_is_paused()` are