fix(agent): use reasoning content when model wraps entire response in think tags

[ygd58]

Fixes #2123

Problem

Some models (especially local Ollama models with extended thinking) wrap their entire response in <think> tags. Hermes detects this as empty content, retries 3 times, then dies with "Max retries (3) for empty content exceeded."

Fix

When max retries are hit and reasoning text is available but final_response is empty, use the reasoning text as the final response instead of dying. This allows the agent to continue working even when the model puts content in think blocks.

Before

❌ Max retries (3) for empty content exceeded. → agent dies

After

Using reasoning as response content (model wrapped entire response in think tags). → agent continues

[ygd58]

Closing — upstream already includes this fix in the latest main. The reasoning-as-fallback logic is now part of the codebase.