M3 WIP: DSI bring-up + state machine + identity overlay

DSI / panel:
- LDO_VO3 acquired at 2500 mV (VDD_MIPI_DPHY) — without this the PHY
  PLL busy-waits forever inside esp_lcd_new_dsi_bus.
- PSRAM bumped to 200 MHz (CONFIG_IDF_EXPERIMENTAL_FEATURES) to keep
  the DPI fed without underruns.
- Pi-7"-style 800x480 panel init (REG_POWERON, PORTA/PORTB/PWM/PORTC)
  + 16-bit RGB565 framebuffer with portrait-mode rotation buffer in
  PSRAM. Currently shows garbled output — known issue, next commit
  switches to the TC358762-bridge-aware init sequence.

State + UX:
- viewport_state simplified to AWAKE/ASLEEP only; "unconfigured" is
  a flag, not a state. Tap always toggles; content choice (identity
  vs frame) is driven by the configured flag.
- BOOT button arms a 15 s identity overlay via local_screens_overlay;
  expired callback returns to prior state.
- Boot-done indicator: two backlight flashes (no usable LED GPIO on
  the Waveshare board — GPIO 35 BOOT is shared with EMAC TXD1).
- Best-effort subsystem init in app_main; display init deferred to
  its own task so a panel hang can't block networking.

Display test pattern: solid R/G/B for 2 s each on boot to characterize
the garble independent of text rendering.

1 files changed, 7 insertions, 3 deletions

diff --git a/main/touch.c b/main/touch.c
index f13183d..4d8003f 100644
--- a/main/touch.c
+++ b/main/touch.c
@@ -10,6 +10,7 @@
 #include "freertos/task.h"
 
 #include "display.h"
+#include "local_screens.h"
 #include "state_machine.h"
 #include "viewport_state.h"
 
@@ -80,10 +81,13 @@ static void touch_task(void *arg)
 
             if (dt_ms > 0 && dt_ms <= TAP_MAX_MS) {
                 last_tap_us = now;
-                viewport_run_state_t cur = state_machine_current();
+                // Cancel any BOOT-button identity overlay so a tap-to-sleep
+                // doesn't fight the overlay timer trying to restore content.
+                if (local_screens_overlay_active()) local_screens_overlay_dismiss();
                 viewport_run_state_t target =
-                    (cur == VIEWPORT_STATE_AWAKE) ? VIEWPORT_STATE_ASLEEP
-                                                  : VIEWPORT_STATE_AWAKE;
+                    (state_machine_current() == VIEWPORT_STATE_AWAKE)
+                        ? VIEWPORT_STATE_ASLEEP
+                        : VIEWPORT_STATE_AWAKE;
                 ESP_LOGI(TAG, "tap (%lu ms) -> %s", (unsigned long)dt_ms,
                          target == VIEWPORT_STATE_AWAKE ? "wake" : "sleep");
                 state_machine_set_local(target);