Scale plot tab to fill available window space at fullscreen

Removed the QScrollArea wrapper and fixed figure-height calculation.
FigureCanvasQTAgg now fills the tab with an Expanding size policy so
all 8 subplots fit in the visible area at 1920x1200 without scrolling.

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

gui_client.py

@@ -22,7 +22,7 @@ from PyQt5.QtCore import QObject, Qt, pyqtSignal
 from PyQt5.QtGui import QColor, QFont
 from PyQt5.QtWidgets import (
     QApplication, QFormLayout, QGroupBox, QHBoxLayout, QLabel,
-    QLineEdit, QMainWindow, QPushButton, QScrollArea, QSizePolicy,
+    QLineEdit, QMainWindow, QPushButton, QSizePolicy,
     QSpinBox, QStatusBar, QTabWidget, QTreeWidget, QTreeWidgetItem,
     QVBoxLayout, QWidget,
 )
@@ -34,7 +34,6 @@ from matplotlib.figure import Figure
 
 MAX_PLOT_POINTS = 200
 PLOT_COLS       = 2
-PLOT_ROW_INCHES = 3.0
 
 
 # ── TCP reader ────────────────────────────────────────────────────────────────
@@ -273,22 +272,13 @@ class DashboardTab(QWidget):
 class PlotTab(QWidget):
     def __init__(self):
         super().__init__()
-        outer = QVBoxLayout(self)
-        outer.setContentsMargins(0, 0, 0, 0)
-
-        scroll = QScrollArea()
-        scroll.setWidgetResizable(True)
-        outer.addWidget(scroll)
-
-        container = QWidget()
-        inner = QVBoxLayout(container)
-        inner.setContentsMargins(4, 4, 4, 4)
-        scroll.setWidget(container)
+        layout = QVBoxLayout(self)
+        layout.setContentsMargins(4, 4, 4, 4)
 
         self._fig    = Figure(tight_layout=True)
         self._canvas = FigureCanvas(self._fig)
         self._canvas.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
-        inner.addWidget(self._canvas)
+        layout.addWidget(self._canvas)
 
         self._series: dict[str, deque]  = {}   # path → deque[(datetime, float)]
         self._units:  dict[str, str]    = {}   # path → unit string
@@ -330,10 +320,6 @@ class PlotTab(QWidget):
         self._fig.clear()
         self._axes = {}
 
-        height = max(3.0, rows * PLOT_ROW_INCHES)
-        self._fig.set_size_inches(10, height)
-        self._canvas.setMinimumHeight(int(height * self._fig.dpi))
-
         for i, k in enumerate(keys):
             ax = self._fig.add_subplot(rows, cols, i + 1)
             label = k.split(".")[-1]