Clarify instruction file path in README usage documentation

[Copilot]

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

The usage instructions had ambiguous wording that conflated file naming pattern with directory path:

Before:

- Create task-specific `.github/.instructions.md` files in your workspace's `.github/instructions` folder

After:

- Create task-specific `*.instructions.md` files in your workspace's `.github/instructions/` folder (e.g., `.github/instructions/my-csharp-rules.instructions.md`)

Changes

• Updated instructionsUsage template in eng/constants.mjs to clarify file path pattern with concrete example
• Regenerated docs/README.instructions.md via eng/update-readme.mjs

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Type of Contribution

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

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Additional Notes

Per @aaronpowell's clarification: instruction files follow the pattern <name>.instructions.md and live in .github/instructions/ directory.

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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.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Confusing line in README.instructions.md</issue_title>
<issue_description>This line is confusing to me:

Create task-specific .github/.instructions.md files in your workspace's .github/instructions folder

Do the files go in .github/ with names x.instructions.md or do they go in .github/instructions - and if so, with what name?</issue_description>

<agent_instructions>The update will need to be in the constants JS file as the README is generated with the update-readme script.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@aaronpowell Good catch - they go in the `.github/instructions` folder named `.instructions.md`, so you'd have `.github/instructions/my-csharp-rules.instructions.md` as the full path.

I'll get the README updated.</comment_new>

• Fixes Confusing line in README.instructions.md #555

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[Copilot]

Pull request overview

This PR clarifies the ambiguous wording in the README usage instructions for instruction files, resolving confusion about where instruction files should be placed and how they should be named.

Changes:

• Updated the instructionsUsage template in eng/constants.mjs to clarify that instruction files follow the *.instructions.md pattern and should be placed in the .github/instructions/ directory
• Added a concrete example path (.github/instructions/my-csharp-rules.instructions.md) to illustrate the correct usage
• Regenerated docs/README.instructions.md to reflect the updated template

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
eng/constants.mjs	Updated the instructionsUsage template string to replace ambiguous .github/.instructions.md with clearer *.instructions.md pattern and added example path
docs/README.instructions.md	Regenerated documentation reflecting the clarified instruction file path pattern with example