Pipeline controller: plan 2 (hard +, error +50 %), backlog throttle, 2 trajectory workers, stop rules, summaries every 50; budget reserve

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

harness/ledger.py

@@ -35,7 +35,8 @@ def spent(since=None):
 
 
 def check_budget():
-    limit = float(os.environ.get("BUDGET_LIMIT_USD", "45"))
+    # BUDGET_RESERVE_USD: ledger USD kept back (second teacher test later); the guard stops at limit - reserve
+    limit = float(os.environ.get("BUDGET_LIMIT_USD", "45")) - float(os.environ.get("BUDGET_RESERVE_USD", "0"))
     s = spent()
     if s >= limit:
         raise BudgetExceeded(f"cycle spend {s} USD >= limit {limit} USD")