Tool Improvement: Refine write_file schema and description

[mattKorwel]

Overview

Part of the tool augmentation effort to optimize tool definitions for Gemini 3.0.

Proposed Changes

Update the write_file tool definition and description based on user modification feedback from the planning session.

Audit and minimize/remove "how-to" sections in tool definitions to optimize the context budget.

Context from Planning

{
  "name": "write_file",
  "description": "Writes content to a specified file in the local filesystem.\n\n      The user has the ability to modify `content`. If modified, this will be stated in the response.",
  "parametersJsonSchema": {
    "properties": {
      "file_path": { "description": "The path to the file to write to.", "type": "string" },
      "content": { "description": "The content to write to the file.", "type": "string" }
    },
    "required": [ "file_path", "content" ],
    "type": "object"
  }
}

Parent: #15331