Add planet environment-extra materials to capex calcs; buildcost.py tool

Every building needs a planet-hazard material bundle on top of its normal
BuildingCosts (SEA for low pressure, HSE for high pressure, MGC for low
gravity, BL for high gravity, INS for cold, TSH for heat - area-scaled
where applicable), confirmed against live in-game build panels on Nike.
FIO's own BuildRequirements field is an unreliable superset across hazard
types, not a direct per-building list - don't use it directly.

- puga/planet.py::environment_extras(): the real threshold table.
- tools/buildcost.py: full construction material list for one building,
  optionally on a given planet.
- Wired into whatif.py/buy.py (via simulate(planet=...)) and scan.py's
  own bcost(), so their capex numbers stop silently omitting this.
- docs/mechanics.md: the rule, plus a separate forum-sourced note on the
  CX order-cancellation penalty.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

puga/simulate.py

@@ -2,6 +2,7 @@
 Input is a PRUNplanner plan JSON (as stored by the API, or built by tools/plan_push.build_payload). Pure given the data passed in.
 Validated against a screenshot of the real simulator (tests/test_simulate.py)."""
 from . import econ
+from . import planet as planet_mod
 
 TIERS = econ.TIERS
 FARMS = {"FRM", "ORC"}
@@ -10,8 +11,8 @@ DEGRADATION_DAYS = 180          # usePlanCalculation.ts: degradation/day = const
 
 def simulate(plan: dict, recipes: list[dict], buildings: list[dict], resources: list[dict], fertility: float,
              price, faction: str | None = None, permits: tuple[float, float] = (1, 2), mcg_per_area: float = 4.0,
-             built: dict[str, int] | None = None) -> dict:
-    """price(ticker, side) -> AIC per unit or None; side is "buy" (net consumed) or "sell" (net produced), like PRUNplanner BUY/SELL exchange preferences; construction uses "buy". resources: planet resources [{material_ticker, resource_type, daily_extraction}]."""
+             built: dict[str, int] | None = None, planet: dict | None = None) -> dict:
+    """price(ticker, side) -> AIC per unit or None; side is "buy" (net consumed) or "sell" (net produced), like PRUNplanner BUY/SELL exchange preferences; construction uses "buy". resources: planet resources [{material_ticker, resource_type, daily_extraction}]. planet: optional, adds environment-extra construction materials via planet.environment_extras() (SEA/HSE/MGC/BL/INS/TSH - needs lowercase pressure/gravity/temperature keys)."""
     d = plan["plan_data"]
     bl = {b["building_ticker"]: b for b in buildings}
     rec = {r["recipe_id"]: r for r in recipes}
@@ -69,7 +70,10 @@ def simulate(plan: dict, recipes: list[dict], buildings: list[dict], resources:
 
     def unit_cost(tk):
         info = bl[tk]
-        return sum(c["material_amount"] * (price(c["material_ticker"], "buy") or 0) for c in info["costs"]) + mcg_per_area * info["area_cost"] * (price("MCG", "buy") or 0)
+        cost = sum(c["material_amount"] * (price(c["material_ticker"], "buy") or 0) for c in info["costs"]) + mcg_per_area * info["area_cost"] * (price("MCG", "buy") or 0)
+        if planet is not None:
+            cost += sum(qty * (price(etk, "buy") or 0) for etk, qty in planet_mod.environment_extras(planet, info["area_cost"]).items())
+        return cost
 
     # Verified vs simulator screenshots: degradation = production buildings' construction cost / 180 (infrastructure excluded);
     # plan cost and area also include one core module (CM), added automatically.