Show steam availability on turbine dashboard

TODO.md

@@ -12,4 +12,4 @@
   - Adjust HX/pressure handling to use stored energy (saturation clamp and pressure rise) and validate steam formation with both pumps at ~3 GW. Use realistic tube-side material assumptions (Inconel 690/SS cladding) and clamp steam quality to phase-equilibrium enthalpy.
   - Update turbine power mapping to consume steam enthalpy/quality and align protection trips with real steam presence; drive inlet steam around 6–7 MPa, quality/enthalpy-based flow to ~550–600 MW(e) per machine class if steam is available.
   - Add integration test: cold start → gens/pumps 2/2 → ramp to ~3 GW → confirm steam quality threshold at the secondary drum → enable all turbines and require electrical output. Include a step that tolerates one secondary pump off for a period to prove redundancy still yields steam.
-- [ ] Dashboard follow-ups: clarify or replace turbine “Steam P” field (currently shows loop pressure, not turbine-driving steam); consider removing it if no better signal is available.
+- [x] Dashboard follow-ups: replace turbine “Steam P” with a more useful steam availability signal (enthalpy × steam flow).

src/reactor_sim/dashboard.py

@@ -490,7 +490,7 @@ class ReactorDashboard:
             [
                 ("Turbines", " ".join(self._turbine_status_lines())),
                 ("Rated Elec", f"{len(self.reactor.turbines)*self.reactor.turbines[0].rated_output_mw:7.1f} MW"),
-                ("Steam P", f"{self._steam_pressure(state):5.2f} MPa"),
+                ("Steam Avail", f"{self._steam_available_power(state):7.1f} MW"),
                 ("Unit1 Elec", f"{state.turbines[0].electrical_output_mw:7.1f} MW" if state.turbines else "n/a"),
                 (
                     "Unit2 Elec",
@@ -733,11 +733,15 @@ class ReactorDashboard:
         lines.append(("Relief valves", ", ".join(reliefs) if reliefs else "Closed"))
         return lines
 
-    def _steam_pressure(self, state: PlantState) -> float:
-        # Only report steam pressure if quality/flow indicate steam is present.
-        if state.secondary_loop.steam_quality < 0.05 or state.secondary_loop.mass_flow_rate < 100.0:
+    def _steam_available_power(self, state: PlantState) -> float:
+        mass_flow = state.secondary_loop.mass_flow_rate * max(0.0, state.secondary_loop.steam_quality)
+        if mass_flow <= 1.0:
             return 0.0
-        return state.secondary_loop.pressure
+        if state.turbines:
+            enthalpy_kjkg = max(0.0, state.turbines[0].steam_enthalpy)
+        else:
+            enthalpy_kjkg = (constants.STEAM_LATENT_HEAT / 1_000.0)
+        return (enthalpy_kjkg * mass_flow) / 1_000.0
 
     def _update_trends(self, state: PlantState) -> None:
         self._trend_history.append((state.time_elapsed, state.core.fuel_temperature, state.core.power_output_mw))