Work through the remaining review items in TODO.md

Keep the HTTP session alive between weather polls (TODO #1). Re-creating the
client each time forced a fresh TLS handshake inside the window where the UI
is frozen. Measured on hardware: the fetch went from ~1.3s to ~80ms, so the
pause is no longer long enough to matter once thermostat controls exist. The
timeout drops from 30s to 10s once a session is warm, since only a cold
handshake needs the longer budget. Any transport error or non-200 tears the
session down so a half-open connection cannot poison every later poll.

The response buffer is now reset per request rather than on
HTTP_EVENT_ON_CONNECTED -- a kept-alive connection does not re-fire that
event, so the buffer would have accumulated across polls.

Indicate stale readings (TODO #2). After two consecutive failures the
temperature dims and the status line shows the age. Age comes from tick
counts, not weather_data_t.last_update: there is no SNTP client here, so
time(NULL) starts at the epoch and any age derived from it is meaningless.

Gate the touch readout behind UI_DEBUG_TOUCH, default off (TODO #3). Kept the
note about LVGL not bubbling events to parents -- it documents a real trap.

Delete main/utils (TODO #4); it had no callers outside itself. Also refreshed
project_structure.txt, which was additionally missing i2c_bus and backlight.

Lay out two 4MB OTA slots (TODO #5) while no devices are fielded, and document
in the README that an OTA download cannot run while the panel is scanning --
the flash write faults the bounce-buffer ISR.

Log the truncation warning once per response instead of once per chunk, and
record the weather task's stack high-water mark (TODO #6): ~2400 bytes spare
of 6144.

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

main/ui/ui_manager.c

@@ -11,10 +11,19 @@ static const char *TAG = "ui_manager";
 
 #define UI_LOCK_TIMEOUT_MS 1000
 
+/*
+ * Bring-up diagnostic: a live readout of the last touch coordinate. Off by
+ * default -- define UI_DEBUG_TOUCH to put it back on screen when working on
+ * the input path.
+ */
+/* #define UI_DEBUG_TOUCH */
+
 static lv_obj_t *temp_label = NULL;
 static lv_obj_t *cond_label = NULL;
 static lv_obj_t *status_label = NULL;
+#ifdef UI_DEBUG_TOUCH
 static lv_obj_t *touch_label = NULL;
+#endif
 
 /*
  * lv_label_set_text() invalidates the label unconditionally, even when the
@@ -37,15 +46,15 @@ static void label_set_if_changed(lv_obj_t *label, const char *text)
 }
 
 /*
- * Live readout of the last contact.
- *
- * Polled from an LVGL timer rather than driven by a widget event. An event
- * handler on the screen object only fires for taps that actually reach the
- * screen: LVGL does not bubble events to parents by default, so anything
- * landing on the header or the temperature card is consumed by that child and
- * never seen here. That made whole regions of the panel look like dead touch
- * zones when the hardware was reporting them perfectly well.
+ * NOTE, even with the readout compiled out: LVGL does not bubble events to
+ * parents by default. An event handler on the screen object never fires for
+ * taps landing on a child widget -- the header or the temperature card
+ * consume them -- which presents as whole regions of the panel being dead to
+ * touch while the hardware reports them perfectly well. Anything that needs
+ * to observe touches screen-wide must poll the input device, as below, rather
+ * than hang an event handler on the screen.
  */
+#ifdef UI_DEBUG_TOUCH
 static void touch_readout_timer_cb(lv_timer_t *timer)
 {
     lv_indev_t *indev = lv_indev_get_next(NULL);
@@ -64,6 +73,7 @@ static void touch_readout_timer_cb(lv_timer_t *timer)
     }
     label_set_if_changed(touch_label, buf);
 }
+#endif
 
 void ui_update_weather(int16_t temp_f, const char *condition)
 {
@@ -80,6 +90,24 @@ void ui_update_weather(int16_t temp_f, const char *condition)
     lvgl_port_unlock();
 }
 
+void ui_set_weather_stale(bool stale)
+{
+    if (!lvgl_port_lock(UI_LOCK_TIMEOUT_MS)) {
+        ESP_LOGW(TAG, "Dropped stale-state update: LVGL lock timed out");
+        return;
+    }
+
+    if (temp_label != NULL) {
+        /* Unlike lv_label_set_text(), setting an identical style value does
+         * not invalidate, so this is safe to call on every poll. */
+        lv_obj_set_style_text_color(temp_label,
+                                    stale ? lv_color_hex(0x5A6672) : lv_color_white(),
+                                    LV_PART_MAIN);
+    }
+
+    lvgl_port_unlock();
+}
+
 void ui_set_status(const char *status)
 {
     if (status == NULL) {
@@ -150,11 +178,13 @@ void ui_init(void)
     lv_label_set_text(status_label, "Starting...");
     lv_obj_set_style_text_color(status_label, lv_color_hex(0x7F8C8D), LV_PART_MAIN);
 
+#ifdef UI_DEBUG_TOUCH
     touch_label = lv_label_create(scr);
     lv_label_set_text(touch_label, "touch  --, --");
     lv_obj_set_style_text_color(touch_label, lv_color_hex(0x3498DB), LV_PART_MAIN);
 
     lv_timer_create(touch_readout_timer_cb, 100, NULL);
+#endif
 
     lvgl_port_unlock();
 

main/ui/ui_manager.h

@@ -1,6 +1,7 @@
 #ifndef UI_MANAGER_H
 #define UI_MANAGER_H
 
+#include <stdbool.h>
 #include <stdint.h>
 #include "lvgl.h"
 
@@ -10,4 +11,11 @@ void ui_init(void);
 void ui_update_weather(int16_t temp_f, const char *condition);
 void ui_set_status(const char *status);
 
+/*
+ * Mark the displayed reading as no longer trustworthy. Dims the temperature
+ * so a value that stopped updating is visibly distinct from a live one,
+ * rather than sitting there at full styling looking current.
+ */
+void ui_set_weather_stale(bool stale);
+
 #endif