fix: meshcore serial connection and battery calculation issues

- Fix _pollUntilConnected overwriting real error with generic timeout
  message — stop polling once backend reaches error state
- Fix battery % calculation: was battery_mv/42 (71% at empty); now
  (battery_mv-3000)/12 for a proper 0-100% LiPo curve
- Improve auto-detect: scan available ports rather than blindly using
  /dev/ttyUSB0; update label to show fallback so users know what to expect
- Add port refresh button (↻) — previously required switching modes
  and back if device was plugged in after panel opened
- Add baud rate selector to serial config strip (default 115200,
  options up to 921600) and wire it through to the connect request

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/js/modes/meshcore.js

@@ -79,6 +79,7 @@ const MeshCore = (function () {
         let body = { transport: _transport };
         if (_transport === 'serial') {
             body.port = document.getElementById('meshcorePortSelect').value || null;
+            body.baud = parseInt(document.getElementById('meshcoreBaudSelect')?.value || '115200', 10);
         } else if (_transport === 'tcp') {
             body.host = document.getElementById('meshcoreTcpHost').value;
             body.port = parseInt(document.getElementById('meshcoreTcpPort').value, 10);
@@ -98,13 +99,20 @@ const MeshCore = (function () {
     function _pollUntilConnected(attempts) {
         if (_connected) return;
         if (attempts > 45) {
-            // Backend retry window (5+15+45s) has elapsed — give up
+            // Backend retry window (5+15+45s) has elapsed — give up only if
+            // the backend hasn't already reported a real error (which would
+            // have been shown by _updateStatusUI and we don't want to overwrite).
+            const dot = document.getElementById('meshcoreStatusDot');
+            if (dot && dot.classList.contains('error')) return;
             _updateStatusUI('error', 'Connection timed out');
             return;
         }
         setTimeout(async () => {
             await _checkStatus();
-            if (!_connected) _pollUntilConnected(attempts + 1);
+            // Stop polling once the backend has settled into a terminal state
+            const dot = document.getElementById('meshcoreStatusDot');
+            const inTerminal = dot && dot.classList.contains('error');
+            if (!_connected && !inTerminal) _pollUntilConnected(attempts + 1);
         }, 2000);
     }
 
@@ -123,7 +131,7 @@ const MeshCore = (function () {
             const sel = document.getElementById('meshcorePortSelect');
             if (!sel) return;
             const current = sel.value;
-            sel.innerHTML = '<option value="">Auto-detect</option>';
+            sel.innerHTML = '<option value="">Auto-detect (/dev/ttyUSB0)</option>';
             (d.ports || []).forEach(p => {
                 const o = document.createElement('option');
                 o.value = p; o.textContent = p;
@@ -133,6 +141,10 @@ const MeshCore = (function () {
         } catch (e) { /* ignore */ }
     }
 
+    async function refreshPorts() {
+        await _loadPorts();
+    }
+
     async function scanBle() {
         const btn = document.querySelector('[onclick="MeshCore.scanBle()"]');
         const sel = document.getElementById('meshcoreBleSelect');
@@ -522,6 +534,7 @@ const MeshCore = (function () {
         connect,
         disconnect,
         selectTransport,
+        refreshPorts,
         scanBle,
         sendMessage,
         switchTab,

templates/partials/modes/meshcore.html

@@ -22,6 +22,13 @@
     <select id="meshcorePortSelect" class="meshcore-strip-select">
       <option value="">Auto-detect</option>
     </select>
+    <button class="meshcore-strip-btn" onclick="MeshCore.refreshPorts()" title="Refresh port list">↻</button>
+    <select id="meshcoreBaudSelect" class="meshcore-strip-select" style="width:90px;">
+      <option value="115200" selected>115200</option>
+      <option value="921600">921600</option>
+      <option value="57600">57600</option>
+      <option value="38400">38400</option>
+    </select>
   </div>
   <div id="meshcoreTcpConfig" class="meshcore-strip-group" style="display:none;">
     <input id="meshcoreTcpHost" type="text" placeholder="Host / IP" value="localhost" class="meshcore-strip-input" style="width:120px;">

utils/meshcore_client.py

@@ -100,7 +100,15 @@ class AsyncWorker:
         cfg = self._config
 
         if isinstance(cfg, SerialConfig):
-            port = cfg.port or "/dev/ttyUSB0"
+            from utils.meshcore import list_serial_ports
+
+            if cfg.port:
+                port = cfg.port
+            else:
+                # Auto-detect: prefer ttyUSB0, then first available port
+                candidates = list_serial_ports()
+                port = next((p for p in candidates if "ttyUSB0" in p), None) or \
+                       (candidates[0] if candidates else "/dev/ttyUSB0")
             self._mc = await MeshCore.create_serial(port=port, baudrate=cfg.baud, debug=False)
             transport, device = "serial", port
         elif isinstance(cfg, TCPConfig):
@@ -205,7 +213,8 @@ class AsyncWorker:
         p = event.payload
         node_id = "self"  # stats_core is always for the local node
         battery_mv = p.get("battery_mv")
-        battery_pct = min(int(battery_mv / 42), 100) if battery_mv else None  # rough: 4200mv = 100%
+        # LiPo linear approximation: 3000mV = 0%, 4200mV = 100%
+        battery_pct = max(0, min(int((battery_mv - 3000) / 12), 100)) if battery_mv else None
         t = MeshcoreTelemetry(
             node_id=node_id,
             timestamp=datetime.now(timezone.utc),