Migrate extension metadata to plugin.json and enforce conventions

[aaronpowell]

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 main branch for this pull request.

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Description

This updates the extension install strategy to align with plugin-based extension shipping in copilot-agent-runtime and simplify extension authoring.

Key changes:

• Migrates extension metadata from canvas.json to .github/plugin/plugin.json for all extensions.
• Adds plugin-shipped extension declaration ("extensions": ".") so extension loading matches github/copilot-agent-runtime#9929 behavior.
• Standardizes visuals on a convention-based rule ("logo": "assets/preview.png") and removes x-awesome-copilot screenshot overrides.
• Updates marketplace generation and website extension install UX to prioritize plugin install commands.
• Removes unused pluginRoots from .github/plugin/marketplace.json.
• Updates extension validation workflow and eng/validate-plugins.mjs to enforce the new extension conventions.
• Updates docs (AGENTS.md, CONTRIBUTING.md) with the new extension metadata and validation requirements.

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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): Extension metadata model and validation/website pipeline updates.

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Additional Notes

• Branch was synced with latest main before finalizing.
• Validation checks run successfully with updated conventions (npm run plugin:validate).

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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 migrates canvas extension metadata to plugin manifests and updates the validation + website/marketplace pipelines so extensions are installed via copilot plugin install ...@awesome-copilot rather than URL-based installs.

Changes:

• Updates website extension UI to copy a plugin install command by default (with URL copy as fallback).
• Standardizes extension plugin manifests (e.g., logo: assets/preview.png, extensions: ".") and publishes extension manifests into .github/plugin/marketplace.json.
• Extends build/validation scripts to treat extensions as plugin sources, enforce new extension conventions, and materialize curated plugin extension references.

Show a summary per file

File	Description
website/src/scripts/pages/extensions.ts	Updates extension details modal + click handlers to copy install command and/or install URL.
website/src/scripts/pages/extensions-render.ts	Renders “Copy Install” and “Copy URL” buttons with data-install-command support.
website/src/pages/extensions.astro	Updates install instructions to prefer plugin install commands.
extensions/where-was-i/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/site-studio/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/release-notes-showcase/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/java-modernization-studio/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/gesture-review/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/feedback-themes/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/diagram-viewer/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/color-orb/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/chromium-control-canvas/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/backlog-swipe-triage/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/arcade-canvas/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
extensions/accessibility-kanban/.github/plugin/plugin.json	Migrates extension metadata to plugin conventions (logo, extensions, slugged name).
eng/validate-plugins.mjs	Adds extension manifest validation and curated plugin extension reference validation.
eng/materialize-plugins.mjs	Adds support for copying extension sources into materialized plugins via x-awesome-copilot.extensions.
eng/generate-website-data.mjs	Generates extension install commands and reads extension metadata from .github/plugin/plugin.json.
eng/generate-marketplace.mjs	Generates marketplace entries from both plugins/ and extensions/ (as plugin sources).
CONTRIBUTING.md	Documents new extension metadata requirements and validation expectations.
AGENTS.md	Documents extension metadata conventions and contribution steps.
.github/workflows/validate-canvas-extensions.yml	Updates extension validation workflow to require .github/plugin/plugin.json and enforce new conventions.
.github/plugin/marketplace.json	Updates generated marketplace output to include extension plugin sources and updated local plugin source paths.

Review details

Comments suppressed due to low confidence (1)

eng/validate-plugins.mjs:209

• validatePlugin now sometimes returns an array (early return when plugin.json is missing), but callers always destructure an object (const { errors, plugin } = validatePlugin(dir)). This will make errors undefined and then throw when accessing errors.length, breaking validation instead of reporting a clean error list.

  // Rule 1: Must have .github/plugin/plugin.json
  const pluginJsonPath = path.join(pluginDir, ".github/plugin", "plugin.json");
  if (!fs.existsSync(pluginJsonPath)) {
    errors.push("missing required file: .github/plugin/plugin.json");
    return errors;
  }

• Files reviewed: 23/23 changed files
• Comments generated: 1
• Review effort level: Low