Cleaning up some legacy around chat modes

[aaronpowell]

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

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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

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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 pull request removes legacy references to "chat modes" and replaces them with the unified "agents" terminology across documentation, configuration files, and tooling scripts. The PR is part of an effort to standardize nomenclature and clean up deprecated concepts in the awesome-copilot repository.

Changes:

• Deleted the deprecated suggest-awesome-github-copilot-chatmodes.prompt.md file
• Updated terminology from "chat modes" to "agents" and "skills" throughout documentation
• Removed "chat-mode" kind from collection and code generation logic
• Updated project guidelines and contribution templates to reflect current terminology

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
prompts/suggest-awesome-github-copilot-chatmodes.prompt.md	Deleted deprecated prompt file for suggesting chat modes
package.json	Updated description and keywords to replace "chat modes" with "skills"
eng/update-readme.mjs	Removed chat-mode logic from collection generation and updated comments
docs/README.prompts.md	Removed entry for deleted chatmodes prompt
docs/README.collections.md	Updated collection description to use "agents" instead of "chat modes"
collections/awesome-copilot.md	Updated description and removed chatmodes prompt entry, updated item count from 6 to 5
collections/awesome-copilot.collection.yml	Removed chatmodes prompt item and updated description
README.md	Updated multiple references from "chat modes" to "agents" and "skills"
CONTRIBUTING.md	Updated all documentation references from "chat modes" to "agents"
.github/pull_request_template.md	Updated checklist items from "chat mode" to "agent"
.github/copilot-instructions.md	Updated file guide section headers and requirements from "Chat Mode" to "Agent"

[Copilot]

Grammar issue: "a agent" should be "an agent" since "agent" starts with a vowel sound. Additionally, the value "Plan" should be lowercase "plan" for consistency with the other lowercase values "agent" and "ask".

Suggested change

	- [ ] The prompt has a `agent` field specified of either `agent`, `ask`, or `Plan`.
	- [ ] The prompt has an `agent` field specified of either `agent`, `ask`, or `plan`.