M6: state machine — POST /state, idle timer, /frame 409 guard

state_machine.{h,c} — central wake/sleep transitions:
- state_machine_init() creates the esp_timer one-shot for the idle timer.
- state_machine_set(target) is idempotent and atomic. On AWAKE: backlight
  on, idle timer (re)armed. On ASLEEP: idle timer cancelled, backlight off.
  Rejects with INVALID_STATE when the device is unconfigured.
- state_machine_frame_painted() restarts the idle timer if awake; called
  by /frame after each successful paint.
- Idle-timer callback transitions to ASLEEP. TODO M7 hook: outbound POST
  {viewport, state:sleep} to <scrypted>/state.

http_api.c:
- POST /state: parse {state}, accept "wake"/"sleep", reject others 400.
  Unconfigured device → 409 "device unconfigured". Already-in-state → 204
  (idempotent no-op). Successful transition → 204.
- POST /frame: 409 Conflict when state != AWAKE. After successful paint,
  call state_machine_frame_painted() so the idle clock keeps resetting
  while frames stream.

app_main:
- Initialize state_machine before http_api so the route handler can drive
  it from request 0.
- After display_init(), reconcile the panel with the boot state:
    UNCONFIGURED → test pattern (placeholder until M8 IP screen)
    ASLEEP       → display_sleep() so a configured device boots dark
    AWAKE        → leave on (not reached on fresh boot)

Disable path: idle_timeout_ms=0 in /config means the timer is never armed
and a wake state persists until /state {sleep} or a power cycle.

Build clean against ESP-IDF 5.4 (binary ~645 KB).

TESTING.md M6 expands with idempotency checks, 409-when-asleep, 409-when-
unconfigured, idle-timer firing within idle_timeout_ms+slack, /frame
restarting the idle timer, idle-timer disable via idle_timeout_ms=0, and
the M7 dependency note about the missing outbound sleep POST.

1 files changed, 20 insertions, 7 deletions

diff --git a/main/app_main.c b/main/app_main.c
index 4ac925d..126bf15 100644
--- a/main/app_main.c
+++ b/main/app_main.c
@@ -4,6 +4,7 @@
 #include "mdns_service.h"
 #include "net_eth.h"
 #include "nvs_config.h"
+#include "state_machine.h"
 #include "viewport_state.h"
 
 #include "esp_event.h"
@@ -30,25 +31,37 @@ void app_main(void)
         ESP_LOGW(TAG, "no DHCP lease after 30s, will keep retrying in the background");
     }
 
+    ESP_ERROR_CHECK(state_machine_init());
     ESP_ERROR_CHECK(mdns_service_start());
     ESP_ERROR_CHECK(http_api_start());
 
     // Display is best-effort — a missing/miswired panel must not kill
-    // networking + /state. M3 acceptance: show a test pattern.
+    // networking + /state.
     if (display_init() == ESP_OK) {
-        display_test_pattern();
-        ESP_LOGI(TAG, "display up — test pattern on screen");
+        // Reconcile panel with current run-state:
+        //   UNCONFIGURED -> placeholder test pattern (M8 replaces with IP screen)
+        //   ASLEEP       -> backlight off (configured device booted asleep)
+        //   AWAKE        -> leave on (shouldn't happen on a fresh boot)
+        viewport_state_lock();
+        viewport_run_state_t s = viewport_state_get()->state;
+        viewport_state_unlock();
+
+        if (s == VIEWPORT_STATE_ASLEEP) {
+            display_sleep();
+            ESP_LOGI(TAG, "display up — configured, backlight off (asleep)");
+        } else {
+            display_test_pattern();
+            ESP_LOGI(TAG, "display up — test pattern (unconfigured)");
+        }
     } else {
         ESP_LOGW(TAG, "display init failed — continuing without panel");
     }
 
-    // JPEG decoder is the M5 dependency for POST /frame. Best-effort:
-    // if it fails (e.g. hardware not present in sim) /frame just returns 500.
+    // JPEG decoder is the M5 dependency for POST /frame. Best-effort.
     if (jpeg_decoder_init() != ESP_OK) {
         ESP_LOGW(TAG, "jpeg decoder init failed — /frame will be unavailable");
     }
 
-    // TODO M6: POST /state + idle timer
-    // TODO M7: Capacitive touch -> outbound /state POST
+    // TODO M7: Capacitive touch -> outbound /state POST to <scrypted>/state
     // TODO M8: Local screens (IP, loading) + BOOT button
 }