Fix backtick back button to work reliably, improve Terminal Shell responsiveness, enhance HID Injector feedback

src/modules/hidinjector.cpp

@@ -21,12 +21,13 @@ public:
   void onEnter() override {
     active = false;
     sent = 0;
-    say("HID ready, plug USB host");
+    say("HID ready");
 #ifdef HAVE_TINYSB
     if (tud_mounted()) {
       active = true;
       sent = 0;
-      say("Host detected - injecting");
+      say("Host detected!");
+      say("Injecting...");
     }
 #endif
   }

src/modules/terminalemu.cpp

@@ -43,10 +43,13 @@ public:
 
   void tick() override {
     if (!connected) return;
-    while (ser.available()) {
+    uint32_t start = millis();
+    while (ser.available() && millis() - start < 10) {
       char c = ser.read();
-      if (rxPos < sizeof(rxBuffer) - 1) rxBuffer[rxPos++] = c;
-      if (rxPos >= sizeof(rxBuffer) - 1) rxPos = sizeof(rxBuffer) - 1;
+      if (rxPos < sizeof(rxBuffer) - 1) {
+        rxBuffer[rxPos++] = c;
+        if (c == '\n') rxPos = 0;
+      }
     }
   }