fix: prevent title generation from hanging with Gemini 3 models

[dgageot]

When using Gemini 3 models (e.g., gemini-3-flash-preview), title generation would hang because thinking was not being properly disabled. The low max_tokens (20) used for title generation left no room for thinking tokens, causing the API to hang.

Changes:

• Set ThinkingBudget=0 in Gemini client when ModelOptions.Thinking() is false, which completely disables thinking at the API level
• Add 30-second timeout to title generation as a safety net
• Fix FromModelOptions to preserve the thinking setting when cloning providers

Assisted-By: cagent

[github-actions]

Code Review Summary

✅ No bugs found in the changed code.

This PR properly addresses the Gemini 3 model hanging issue by:

1. Correctly implementing thinking override logic - The new buildConfig() code properly checks if thinking is explicitly disabled via ModelOptions.Thinking() and sets ThinkingBudget=0 before falling back to config-based thinking settings

2. Proper nil safety - All pointer dereferences are guarded with nil checks (e.g., thinking != nil && !*thinking)

3. Good context management - The timeout in generator.go correctly wraps the entire title generation operation with proper cleanup via defer cancel()

4. Complete fix for FromModelOptions - The thinking option is now properly preserved when cloning providers

5. Comprehensive test coverage - Tests cover all three scenarios: thinking explicitly disabled, explicitly enabled, and not set

The implementation is well-documented and follows Go best practices for pointer handling, context management, and error prevention.