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>

CLAUDE.md

@@ -28,11 +28,14 @@ make lint typecheck
 
 ## Gotchas
 
-- **ESP-IDF is not yet installed on this machine** — install instructions in AGENTS.md.
-- The firmware scaffold has never been built; treat BSP calls and sdkconfig as
-  provisional until first successful `idf.py build` (see warning in AGENTS.md).
-- The device flashes over USB-C on this server, but it doesn't currently enumerate
-  (`/dev/ttyACM*` empty) and this user lacks the `dialout` group — resolve both before
-  attempting to flash.
+- ESP-IDF v5.5 lives at `~/esp-idf` (`source ~/esp-idf/export.sh`). Flash via
+  `sg dialout -c …` (see AGENTS.md) — the login session predates dialout membership.
+- **PSRAM 200 MHz requires `CONFIG_IDF_EXPERIMENTAL_FEATURES=y`** — without it the
+  option silently degrades to 20 MHz and the DSI display underruns into a watchdog
+  loop. Details in AGENTS.md.
 - Gateway speech deps are optional extras; `make setup` alone runs the app and tests
-  without GPU/ML packages.
+  without GPU/ML packages. `make setup` uses `python3.12` (system python3 is 3.8).
+- Tatlock replies open with a `<think>` block — always strip via
+  `tatlock.strip_reasoning()` before TTS or display.
+- Low power is a prime user requirement: see "Power management" in
+  docs/architecture.md before touching the face/render loop.