fix: honor gateway agent max turns config

[kchuang1015]

Summary

• Resolve gateway-created agent max iterations from config first (agent.max_turns, then legacy top-level max_turns)
• Keep HERMES_MAX_ITERATIONS as a legacy fallback only
• Prevent stale dotenv reloads from overriding the configured gateway loop limit

Test Plan

• python3 -m pytest -q tests/gateway/test_agent_max_turns_config.py
• python3 -m py_compile gateway/run.py tests/gateway/test_agent_max_turns_config.py

[kshitijk4poor]

Closing as already resolved on current main.

The config-authority contract this PR restores is already in place in gateway/run.py:

• _reload_runtime_env_preserving_config_authority() reloads .env for fresh credentials but explicitly preserves config.yaml's agent.max_turns so a stale HERMES_MAX_ITERATIONS in .env can't override it on later turns.
• _bridge_max_turns_from_config() bridges config.yaml agent.max_turns into the env var, and the startup bridge guards the "stale 60 vs configured 500" regression.
• _current_max_iterations() re-reads the budget per turn after that refresh.

So a stale HERMES_MAX_ITERATIONS=90 no longer wins over a higher configured agent.max_turns. Thanks for the fix and the clear write-up of the regression — the contract you wanted is honored on main.