feat(budget): make tool result persistence thresholds configurable

Add BudgetConfig dataclass to centralize and make overridable the
hardcoded constants (50K per-result, 200K per-turn, 2K preview) that
control when tool outputs get persisted to sandbox. Configurable at
the RL environment level via HermesAgentEnvConfig fields, threaded
through HermesAgentLoop to the storage layer.

Resolution: pinned (read_file=inf) > env config overrides > registry
per-tool > default. CLI override: --env.turn_budget_chars 80000

environments/benchmarks/yc_bench/yc_bench_env.py

@@ -549,6 +549,7 @@ class YCBenchEvalEnv(HermesAgentBaseEnv):
                 temperature=self.config.agent_temperature,
                 max_tokens=self.config.max_token_length,
                 extra_body=self.config.extra_body,
+                budget_config=self.config.build_budget_config(),
             )
             result = await agent.run(messages)