fix: plan agent file with up to date format to use with Copilot CLI

[VeVarunSharma]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• [] My contribution adds a new instruction, prompt, or chat mode file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, or chat mode with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.

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Description

This update ensures that this agent file works with the the Copilot CLI. After attempting to use it with the Copilot CLI it was initially broken but it now works on the Copilot CLI mode!

Copilot CLI still does not have Plan mode natively so having a proper agent file that folks can use is important for now until a native plan mode feature is released. There's an Issue for that here: github/copilot-cli#783

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Type of Contribution

• New instruction file.
• New prompt file.
• New chat mode file.
• New collection file.
• Update to existing instruction, prompt, chat mode, or collection.
• Other (please specify):

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Additional Notes

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.

[Copilot]

Pull request overview

This PR updates the plan.agent.md file to use a YAML-based tools format compatible with Copilot CLI, replacing the previous JSON array format. The update includes migrating tool names to use namespace prefixes (e.g., search/codebase, vscode/extensions) and removing the deprecated findTestFiles tool and its associated documentation reference.

Key Changes:

• Converted tools specification from JSON array to YAML list format
• Added namespace prefixes to tool names for Copilot CLI compatibility
• Removed findTestFiles tool from both front matter and content

[Copilot]

The front matter is missing the model field. According to AGENTS.md, it's strongly recommended to specify the model field for agent files. Consider adding a line like model: GPT-4.1 (or the appropriate model this agent is optimized for) after the name field.

[Copilot]

The content references the search tool on line 33, but this tool is not listed in the front matter tools array. Looking at other agent files like janitor.agent.md, both search and namespaced search tools like search/searchResults should be included separately. Consider adding - search to the tools list in the front matter, or update the content to reference the specific search tool that's available.