First successful flash: placeholder face live; fix 20MHz PSRAM trap; power ladder

- firmware boots to a rendered LVGL face in 1.57s (eyes + smile + tag)
- sdkconfig: CONFIG_IDF_EXPERIMENTAL_FEATURES=y unlocks SPIRAM 200MHz
  (silently degraded to 20MHz before -> MIPI-DSI underrun -> LVGL lock
  starvation -> task watchdog); mirrors official 08_lvgl_demo_v9 config
- architecture.md: power management section (user prime concern) —
  active/ambient/dormant/night ladder, levers, hard edges, <=300ms wake
- AGENTS/CLAUDE: replace stale bring-up warnings with verified commands

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

AGENTS.md

@@ -52,27 +52,27 @@ LVGL timers).
   `examples/esp-idf/` — notably `08_lvgl_demo_v9` (display), `06_I2SCodec` (audio),
   `04_wifistation` (Wi-Fi via ESP-Hosted). When wiring a new peripheral, check the
   official example first; do not guess pin mappings.
-- ⚠️ **Unverified scaffold**: the BSP API calls in `desklock_main.c` and the
-  `sdkconfig.defaults` values were written before the first successful build. Validate
-  against the official examples on first bring-up, then delete this warning.
-
 ```bash
-# One-time: install ESP-IDF (not yet installed on tower-of-joy)
-git clone -b v5.5 --recursive https://github.com/espressif/esp-idf.git ~/esp-idf
-~/esp-idf/install.sh esp32p4
-
-# Every shell:
+# ESP-IDF v5.5 is installed at ~/esp-idf. Every shell:
 source ~/esp-idf/export.sh
 
-# Build / flash / monitor (device is on USB-C; check `ls /dev/ttyACM*`)
+# Build / flash (device on USB-C at /dev/ttyACM0, CH343 bridge)
 cd firmware
-idf.py set-target esp32p4        # once
 idf.py build
-idf.py -p /dev/ttyACM0 flash monitor   # Ctrl+] exits monitor
+sg dialout -c "bash -lc 'source ~/esp-idf/export.sh >/dev/null && idf.py -p /dev/ttyACM0 flash'"
 ```
 
-Flashing requires the `dialout` group (or run with sudo once and fix the group). If the
-device doesn't enumerate, hold BOOT while pressing RESET to enter download mode.
+- `sg dialout -c '…'` is needed because the login session predates the user's dialout
+  membership; a plain `idf.py flash` works after any re-login.
+- **PSRAM must run at 200 MHz** or the 800×800 MIPI-DSI framebuffer underruns
+  (`lcd.dsi.dpi: can't fetch data…` spam, LVGL lock never frees, task watchdog).
+  `CONFIG_SPIRAM_SPEED_200M` only takes effect together with
+  `CONFIG_IDF_EXPERIMENTAL_FEATURES=y` — otherwise it is **silently dropped** and you
+  get 20 MHz. `sdkconfig.defaults` mirrors the official `08_lvgl_demo_v9` config.
+- Non-interactive boot-log capture (avoid `idf.py monitor`, it's interactive): open
+  `/dev/ttyACM0` at 115200 with pyserial, pulse RTS to reset, read ~8 s. Verified boot
+  is ~1.6 s from reset to `desklock: DeskLock up`.
+- If the device doesn't enumerate, hold BOOT while pressing RESET for download mode.
 
 ## Gateway (`gateway/`)