Summary

• detect thinking-budget exhaustion for chat-completions responses that return structured reasoning fields without visible text
• record usage before length/empty-response recovery so Hermes can use real token pressure for recovery decisions
• compact context before continuation/prefill when a reasoning-only response already shows the conversation is over the compaction threshold
• add regression tests for structured reasoning truncation and proactive compression retry paths

Root Cause

Hermes already had a thinking-budget guard for inline <think> content, but OpenAI-compatible models like glm-5-turbo often return reasoning via reasoning_content/reasoning_details with empty content. Those responses skipped the guard, then walked into continuation or prefill retries that grew context further without ever giving compression a chance.

Notes

• This PR focuses on the still-real structured-reasoning recovery gap from [Bug] Thinking model (glm-5-turbo) reasoning tokens exhaust output budget, producing empty responses with no recovery path #9344.
• The separate stale _last_content_with_tools fallback issue from [Bug]: _last_content_with_tools fallback bypasses empty-response retries, causing silent agent loop termination mid-task #7968 is tracked independently in Bugfix: avoid stale tool-turn fallback on empty responses #9432 and is intentionally not duplicated here.

Validation

• git diff --check
• python3 -m py_compile run_agent.py tests/run_agent/test_run_agent.py
• Full pytest was not runnable locally in this environment because the machine does not currently have the repo's required Python 3.11 + dev test toolchain installed.

Closes #9344