P1: PySide6 + pyqtgraph GUI shell (PID browser + live overlay plot)

First graphical frontend on obdcore. Cross-platform (Win/mac/Linux).

- gui/controller.py: owns link/registry/store/scheduler; subscribe == poll ==
  plot; per-PID rates (ICP/FICM/RPM fast); optional CSV recording.
- gui/main.py: connection bar (port dropdown via find_ports, baud, Mock,
  connect), left PID browser grouped by system with live values + confidence
  badges + checkboxes, central pyqtgraph overlay plot with legend, Normalize
  (% of range) toggle for mixed-scale PIDs, Crank/Driving/Vitals presets,
  10Hz refresh reading the store off the acquisition thread.
- run_gui.py launcher; requirements-gui.txt.
- store.py: lock Channel push/series (GUI reads while scheduler writes).
- docs/gui-p1-preview.png: validated render (mock crank, ICP ramp to 540).

Validated headless (offscreen Qt): connect(mock) -> crank preset -> ICP
streams past 500 -> normalize -> uncheck removes curve -> clean disconnect.
obdcore tests still pass after the locking change.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs

obdcore/store.py

@@ -10,7 +10,11 @@ from collections import deque
 
 
 class Channel:
-    """One PID's rolling history plus session min/max."""
+    """One PID's rolling history plus session min/max.
+
+    Lock-guarded so the acquisition thread can push while the GUI thread
+    reads series()/snapshots without a 'deque mutated during iteration' race.
+    """
 
     def __init__(self, key, maxlen=3600):
         self.key = key
@@ -19,22 +23,27 @@ class Channel:
         self.hi = None
         self.last_t = None
         self.last_v = None
+        self._lock = threading.Lock()
 
     def push(self, t, v):
-        self.buf.append((t, v))
-        self.last_t, self.last_v = t, v
-        if v is not None:
-            self.lo = v if self.lo is None else min(self.lo, v)
-            self.hi = v if self.hi is None else max(self.hi, v)
+        with self._lock:
+            self.buf.append((t, v))
+            self.last_t, self.last_v = t, v
+            if v is not None:
+                self.lo = v if self.lo is None else min(self.lo, v)
+                self.hi = v if self.hi is None else max(self.hi, v)
 
     def reset_minmax(self):
-        self.lo = self.hi = self.last_v
+        with self._lock:
+            self.lo = self.hi = self.last_v
 
     def series(self, since=None):
         """Return [(t, v), ...]; if since given, only samples with t >= since."""
+        with self._lock:
+            items = list(self.buf)          # snapshot under lock
         if since is None:
-            return list(self.buf)
-        return [(t, v) for (t, v) in self.buf if t >= since]
+            return items
+        return [(t, v) for (t, v) in items if t >= since]
 
 
 class TimeSeriesStore: