Text triggers override explicit UI settings for thinking mode

Bug Description

When a user explicitly selects thinking mode via tab-completion (which sets max_thinking_length: 31999), typing the word "think" in the next message overrides this setting back to max_thinking_length: 1024.

Steps to Reproduce

1. Press tab to autocomplete "thinking mode" (sets limit to 31999)
2. Type a message containing the word "think"
3. Observe system prompt shows max_thinking_length: 1024 instead of 31999

Expected Behavior

Explicit UI selections should take precedence over text-based inference. Once a user has explicitly chosen thinking mode via UI, natural language keywords shouldn't override that choice.

Actual Behavior

Text triggers silently override explicit user configuration choices.

Impact

Users lose control over their explicitly chosen settings, making it difficult to use higher thinking limits when discussing thinking itself.