Put sidebar controls in fragment to prevent page blanking

Both controls and display are now fragments, so slider
changes don't trigger full page reruns.

src/py_dvt_ate/app/dashboard/app.py

@@ -16,9 +16,6 @@ from py_dvt_ate.simulation.physics.engine import PhysicsEngine
 # History buffer size for charts
 HISTORY_SIZE = 500
 
-# Simulation speed settings
-DEFAULT_TIME_MULTIPLIER = 10.0  # 10x faster than real-time
-
 
 @dataclass
 class SimulationHistory:
@@ -48,17 +45,17 @@ def init_session_state() -> None:
         st.session_state.history = SimulationHistory()
     if "running" not in st.session_state:
         st.session_state.running = False
-    if "time_multiplier" not in st.session_state:
-        st.session_state.time_multiplier = DEFAULT_TIME_MULTIPLIER
     if "last_update" not in st.session_state:
         st.session_state.last_update = time.time()
+    # Note: time_multiplier, temp_setpoint, input_voltage, output_enabled,
+    # load_current are managed by their respective widgets via keys
 
 
 def step_simulation() -> None:
     """Advance the simulation based on elapsed real time and multiplier."""
     engine: PhysicsEngine = st.session_state.engine
     history: SimulationHistory = st.session_state.history
-    multiplier: float = st.session_state.time_multiplier
+    multiplier: float = st.session_state.get("time_multiplier", 10)
 
     # Calculate how much simulation time to advance
     current_time = time.time()
@@ -87,10 +84,18 @@ def step_simulation() -> None:
     history.power_dissipation.append(electrical.power_dissipation)
 
 
-def display_controls() -> None:
+def sync_engine_from_session_state() -> None:
-    """Display simulation control panel in sidebar."""
+    """Sync engine parameters from session state (called by fragment)."""
     engine: PhysicsEngine = st.session_state.engine
+    engine.set_chamber_setpoint(st.session_state.get("temp_setpoint", 25.0))
+    engine.set_input_voltage(st.session_state.get("input_voltage", 5.0))
+    engine.set_output_enabled(st.session_state.get("output_enabled", False))
+    engine.set_load_current(st.session_state.get("load_current", 100.0) / 1000.0)
 
+
+@st.fragment
+def display_controls() -> None:
+    """Display simulation control panel in sidebar (as fragment to avoid full reruns)."""
     st.sidebar.header("Simulation Controls")
 
     # Start/Stop button
@@ -99,14 +104,12 @@ def display_controls() -> None:
             "Stop Simulation", type="primary", use_container_width=True
         ):
             st.session_state.running = False
-            st.rerun()
     else:
         if st.sidebar.button(
             "Start Simulation", type="primary", use_container_width=True
         ):
             st.session_state.running = True
             st.session_state.last_update = time.time()
-            st.rerun()
 
     # Reset button
     if st.sidebar.button("Reset", use_container_width=True):
@@ -114,27 +117,27 @@ def display_controls() -> None:
         st.session_state.history = SimulationHistory()
         st.session_state.running = False
         st.session_state.last_update = time.time()
-        st.rerun()
 
     st.sidebar.divider()
 
     # Time multiplier
     st.sidebar.subheader("Simulation Speed")
-    time_mult = st.sidebar.select_slider(
+    st.sidebar.select_slider(
         "Time Multiplier",
         options=[1, 2, 5, 10, 20, 50, 100],
-        value=int(st.session_state.time_multiplier),
+        value=10,
         format_func=lambda x: f"{x}x",
-        key="time_mult_slider",
+        key="time_multiplier",
+    )
+    st.sidebar.caption(
+        f"1 real second = {st.session_state.get('time_multiplier', 10)} simulation seconds"
     )
-    st.session_state.time_multiplier = float(time_mult)
-    st.sidebar.caption(f"1 real second = {time_mult} simulation seconds")
 
     st.sidebar.divider()
 
     # Temperature setpoint
     st.sidebar.subheader("Thermal Chamber")
-    temp_setpoint = st.sidebar.slider(
+    st.sidebar.slider(
         "Temperature Setpoint (C)",
         min_value=-40.0,
         max_value=125.0,
@@ -142,13 +145,12 @@ def display_controls() -> None:
         step=5.0,
         key="temp_setpoint",
     )
-    engine.set_chamber_setpoint(temp_setpoint)
 
     st.sidebar.divider()
 
     # Power supply controls
     st.sidebar.subheader("Power Supply")
-    input_voltage = st.sidebar.slider(
+    st.sidebar.slider(
         "Input Voltage (V)",
         min_value=0.0,
         max_value=12.0,
@@ -156,20 +158,18 @@ def display_controls() -> None:
         step=0.1,
         key="input_voltage",
     )
-    engine.set_input_voltage(input_voltage)
 
-    output_enabled = st.sidebar.toggle(
+    st.sidebar.toggle(
         "Output Enabled",
-        value=engine.is_output_enabled,
+        value=False,
         key="output_enabled",
     )
-    engine.set_output_enabled(output_enabled)
 
     st.sidebar.divider()
 
     # Load controls
     st.sidebar.subheader("Electronic Load")
-    load_current_ma = st.sidebar.slider(
+    st.sidebar.slider(
         "Load Current (mA)",
         min_value=0.0,
         max_value=500.0,
@@ -177,7 +177,6 @@ def display_controls() -> None:
         step=10.0,
         key="load_current",
     )
-    engine.set_load_current(load_current_ma / 1000.0)
 
 
 @st.fragment(run_every=0.1)
@@ -186,6 +185,9 @@ def simulation_display() -> None:
     engine: PhysicsEngine = st.session_state.engine
     history: SimulationHistory = st.session_state.history
 
+    # Sync engine parameters from UI controls
+    sync_engine_from_session_state()
+
     # Step simulation if running
     if st.session_state.running:
         step_simulation()
@@ -220,7 +222,7 @@ def simulation_display() -> None:
         st.metric(
             "Sim Time",
             f"{engine.simulation_time:.1f} s",
-            delta=f"{status} @ {st.session_state.time_multiplier:.0f}x",
+            delta=f"{status} @ {st.session_state.get('time_multiplier', 10):.0f}x",
         )
 
     # Temperature chart