feat: Add MODEL_BEHAVIOR to control tool usage

[google-labs-jules]

This change introduces a new environment variable, MODEL_BEHAVIOR, to control the tool-calling behavior of the AI models. This allows for more granular control over the models' aggressiveness in using tools, and it replaces the less descriptive USE_SPECIFIC_API_FOR_WRITER variable. The getModel function has been updated to return both the model and its behavior, and all agents have been updated to use this new function. System prompts in the task-manager have also been updated to reflect the new MODEL_BEHAVIOR. Additionally, this change adds a new test file to verify the new implementation.

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PR created automatically by Jules for task 4975261186171057335 started by @ngoiyaeric

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Project	Deployment	Preview	Comments	Updated (UTC)
qcx	Error			Nov 11, 2025 11:30pm

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