Add visual-pr plugin — screenshot capture, annotation, and PR embedding (#1804)

* Add visual-pr plugin: screenshot capture, annotation, PR embedding, and screen recording

Four skills that teach Copilot to capture UI screenshots (Playwright + PIL),
annotate them with algorithmic label placement, embed before/after images
in PR descriptions, and record animated GIF demos.

Includes demo images showing the annotation engine on GitHub Issues.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Update generated README tables and marketplace.json

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Embed annotate.py module in image-annotations skill

The full working module (annotate_image, grid_image, diff_images) is now
included as a code block so users can save it as annotate.py and import
directly. Scrubbed project-specific labels from examples.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* Address review feedback: mss.mss() context manager, fix RECT struct, consistent placeholder

- Use mss.mss() context manager instead of mss.MSS() (ui-screenshots, screen-recording)
- Fix broken RECT struct in window+GIF combining example (screen-recording)
- Consistent projectId placeholder in AzDO upload example (pr-screenshots)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.github/plugin/marketplace.json

@@ -792,6 +792,12 @@
       "description": "Comprehensive collection of prompts, instructions, and resources for building declarative agents and API plugins using TypeSpec for Microsoft 365 Copilot extensibility.",
       "version": "1.0.0"
     },
+    {
+      "name": "visual-pr",
+      "source": "visual-pr",
+      "description": "Capture, annotate, and embed screenshots and animated GIF demos in pull request descriptions. Includes Playwright-based UI capture, PIL image annotations, PR embedding workflows for GitHub and Azure DevOps, and screen recording with variable timing.",
+      "version": "1.0.0"
+    },
     {
       "name": "whatidid",
       "description": "Turn your Copilot sessions into proof of impact — research-grounded HTML reports with effort estimation, skills analysis, and ROI metrics from local session logs.",