Add pptify-plugin (editable PPTX; refactored for feedback #1848)

[kimtth]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• I have read and followed the Guidance for submissions involving paid services.
• My contribution adds a new instruction, prompt, agent, skill, workflow, or canvas extension 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, agent, skill, workflow, or canvas extension with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.
• I am targeting the staged branch for this pull request.

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Description

Adds the pptify plugin for PowerPoint deck authoring with GitHub Copilot. The plugin helps users plan, specify, review, and improve presentation decks through Copilot-native guidance rather than a bundled runtime generator.

This submission is refactored in response to feedback from #1848. The earlier version was reviewed as too specific for this repository and too dependent on external runtime code. This version narrows the contribution to repository-native Copilot assets:

• removed bundled PPTX runtime code, setup scripts, install steps, and external tool execution paths;
• moved content into the official awesome-copilot source layout with one top-level agent and five top-level skills;
• changed reference-deck analysis and visual/tooling guidance into documentation-only workflows;
• kept external tools optional and user-directed rather than installed, configured, or run by the plugin;

Agent

• pptify-slides-builder - guides the end-to-end PowerPoint deck workflow, including narrative strategy, slide planning, coordinate-explicit slide specification, visual direction, and quality review.

Skills

• pptify-context-prep - prepares narrative framework, source material, audience needs, constraints, and bundled design profiles before authoring a deck spec.
• pptify-slide-spec - helps author or repair coordinate-explicit deck specs, including layout groups, objects, bounding boxes, tables, images, lines, shapes, and collision-safe content.
• pptify-visual-assets - provides guidance for planning and placing icons, images, SVGs, infographics, and other visual assets in deck layouts.
• pptify-reference-deck-analysis - documents reference PPTX analysis workflows for extracting reusable structure, style, and layout signals from existing decks.
• pptify-quality-gates - validates and repairs deck specs and PPTX outputs against audit criteria such as collisions, overflow, hierarchy, asset layering, and reference-deck alignment.

Validation completed locally:

npm run plugin:validate
npm run build

Both commands completed successfully, and pptify was validated as a plugin. The pptify-* skills also validate successfully. The current staged branch has an unrelated pre-existing skill:validate failure in aws-cloudwatch-investigation due to an invalid skill name.

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Type of Contribution

• New instruction file.
• New prompt file.
• New agent file.
• New plugin.
• New skill file.
• New agentic workflow.
• New canvas extension.
• Update to existing instruction, prompt, agent, plugin, skill, workflow, or canvas extension.
• Other (please specify):

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Additional Notes

This PR is intended to address the #1848 maintainability concern directly: the plugin no longer bundles or runs the previous PPTX generation runtime. It now contributes reusable Copilot guidance for deck planning, slide specification, visual asset planning, reference analysis, and quality review.

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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.

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