handshake-capture-c6: SPI bus lock, SD v1.0.2 diagnostics, MUST_DO review

- SPI_Bus_Lock: serialize LCD + SD on shared SPI; pause display during SD
- SD_Init after WiFi scan; SD_IsReady gating; serial [SD]/[CAP] diagnostics
- MUST_DO_IMPROVEMENTS.md full firmware review backlog; README link
- Bump HANDSHAKE_FIRMWARE_VERSION to 1.0.2 (header)

Made-with: Cursor

handshake-capture-c6/handshake-capture-c6.ino

@@ -17,8 +17,6 @@ enum CaptureState {
 
 CaptureState captureState = STATE_SCANNING;
 unsigned long capture_start_time = 0;
-// Hard cap per channel visit: should exceed MAX_OBSERVE_CYCLES * (observe + capture).
-const unsigned long CHANNEL_TIMEOUT_MS = 150000UL;
 
 // ─── Live capture visual update ───
 
@@ -119,14 +117,17 @@ void setup() {
   Set_Backlight(100);
   Lvgl_Init();
 
+  // WiFi + scan before SD: shared SPI with LCD; radio init can affect first SD.begin timing.
+  handshakeCaptureInit();
+  WiFiScanner_Refresh();
+
+  HANDSHAKE_LOGLN("[SETUP] mounting SD after WiFi scan");
   if (!SD_Init()) {
     Ui_SetWifiStatus("SD: no card");
   } else {
     Ui_SetWifiStatus("SD OK");
   }
 
-  handshakeCaptureInit();
-  WiFiScanner_Refresh();
   captureState = STATE_SCANNING;
 }
 
@@ -147,8 +148,10 @@ void loop() {
         break;
       }
       if (!SD_IsReady()) {
+        HANDSHAKE_LOGLN("[CAP] SD not ready — calling SD_Init before capture");
         SD_Init();
         if (!SD_IsReady()) {
+          HANDSHAKE_LOGLN("[CAP] BLOCKED: SD_IsReady still false — UI: Insert SD card");
           Ui_SetWifiStatus("Insert SD card");
           delay(800);
           break;
@@ -186,7 +189,7 @@ void loop() {
       } else if (!any_active) {
         stopCapture();
         captureState = STATE_SCANNING;
-      } else if (millis() - capture_start_time > CHANNEL_TIMEOUT_MS) {
+      } else if (millis() - capture_start_time > HANDSHAKE_CHANNEL_TIMEOUT_MS) {
         Ui_SetWifiStatus("Ch timeout");
         stopCapture();
         captureState = STATE_SCANNING;