test: freeze the exact budget fixture used by the runtime

Derive synthetic terrain metadata from the fixture and copy the same bytes that were hashed before building.

Co-authored-by: Codex <codex@openai.com>

tools/airdef.py

@@ -169,7 +169,7 @@ def test_budgets():
         "schema": 1,
         "command": "test-budgets",
         "scenario": BUDGET_SCENARIO,
-        "scenario_render_world": "flat at y=64",
+        "scenario_render_world": None,
         "status": "failed",
         "exit_code": None,
         "scenario_counts": {"scripts": 1, "steps": None, "raid_requests": None,
@@ -212,7 +212,11 @@ def test_budgets():
         wasmtime = re.search(r'\[\[package\]\]\s*name = "wasmtime"\s*version = "([^"]+)"', lock_text)
         report["wasmtime_version"] = wasmtime.group(1) if wasmtime else None
         fixture = ROOT / "airdef-mod" / BUDGET_SCENARIO
-        fixture_text = fixture.read_text()
+        fixture_bytes = fixture.read_bytes()
+        fixture_text = fixture_bytes.decode("utf-8")
+        flat_heights = list(dict.fromkeys(re.findall(r"(?m)^render-ground-y\s*=\s*(-?\d+)\s*$", fixture_text)))
+        if flat_heights:
+            report["scenario_render_world"] = "flat at y=" + ",".join(flat_heights)
         counts = report["scenario_counts"]
         counts["steps"] = len(re.findall(r"(?m)^\[\[step\]\]$", fixture_text))
         counts["air_defense_units"] = len(re.findall(r'(?m)^command = "airdef deploy [^"]+"', fixture_text))
@@ -221,7 +225,7 @@ def test_budgets():
         counts["raid_units_requested"] = sum(map(int, requests))
         for field in ("ticks", "frames"):
             counts[field] = sum(map(int, re.findall(rf"(?m)^{field}\s*=\s*(\d+)\s*$", fixture_text)))
-        report["scenario_sha256"] = hashlib.sha256(fixture.read_bytes()).hexdigest()
+        report["scenario_sha256"] = hashlib.sha256(fixture_bytes).hexdigest()
 
         mod()
         artifact = hmod()
@@ -247,7 +251,7 @@ def test_budgets():
         with tempfile.TemporaryDirectory(prefix="airdef-wasm-budget-") as temp:
             isolated = Path(temp)
             (isolated / "tests").mkdir()
-            shutil.copy2(fixture, isolated / "tests" / "wasm_budget.toml")
+            (isolated / "tests" / "wasm_budget.toml").write_bytes(fixture_bytes)
             command = [cargo(), "run", "--locked", "--manifest-path", FORK / "Cargo.toml",
                        "-p", "cargo-horizon-mod", "--", "horizon-mod", "test", "--hmod", artifact, "budget"]
             print("+", " ".join(str(c) for c in command), flush=True)