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/terminalbench_2/terminalbench2_env.py

@@ -541,6 +541,7 @@ class TerminalBench2EvalEnv(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)
             else:
@@ -553,6 +554,7 @@ class TerminalBench2EvalEnv(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)