Add markdown-preview plugin

plugins/markdown-preview/implementation_plan.md

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+# Markdown Preview Plugin
+
+Add a plugin to Elementary Code that allows users to preview rendered markdown in a side-by-side view alongside the editor.
+
+## User Review Required
+
+> [!IMPORTANT]
+> **Rendering Approach**: This plugin will use WebKit (webkit2gtk-4.0) to render the markdown as HTML. The preview will appear in a separate pane that can be toggled on/off. The markdown will be converted to HTML and styled with GitHub-flavored markdown CSS for a clean, familiar appearance.
+
+> [!IMPORTANT]
+> **UI Integration**: The preview will be accessible via:
+> - A toolbar button that appears when editing markdown files
+> - A keyboard shortcut (Ctrl+Shift+M)
+> - The preview pane will appear to the right of the editor in a split view
+
+## Proposed Changes
+
+### Markdown Preview Plugin
+
+A new plugin that provides live markdown rendering capabilities for markdown files.
+
+#### [NEW] [markdown-preview.vala](file:///home/chuck/Dropbox/Programming/Languages_and_Code/Programming_Projects/Programming_Tools/elementary-code-altdistros/plugins/markdown-preview/markdown-preview.vala)
+
+Main plugin implementation with:
+- WebKit WebView for rendering HTML
+- Markdown to HTML conversion using a simple parser
+- Live preview updates as the user types (with debouncing)
+- Split pane integration with the editor
+- Toggle button in toolbar for showing/hiding preview
+- Keyboard shortcut (Ctrl+Shift+M) support
+- Auto-scroll synchronization between editor and preview
+- GitHub-flavored markdown CSS styling
+
+#### [NEW] [markdown-preview.plugin](file:///home/chuck/Dropbox/Programming/Languages_and_Code/Programming_Projects/Programming_Tools/elementary-code-altdistros/plugins/markdown-preview/markdown-preview.plugin)
+
+Plugin metadata file describing the plugin name, description, and author information.
+
+#### [NEW] [meson.build](file:///home/chuck/Dropbox/Programming/Languages_and_Code/Programming_Projects/Programming_Tools/elementary-code-altdistros/plugins/markdown-preview/meson.build)
+
+Build configuration for the markdown-preview plugin, including webkit2gtk-4.0 dependency.
+
+---
+
+### Plugin Registration
+
+#### [MODIFY] [meson.build](file:///home/chuck/Dropbox/Programming/Languages_and_Code/Programming_Projects/Programming_Tools/elementary-code-altdistros/plugins/meson.build)
+
+Add `subdir('markdown-preview')` to register the new plugin in the build system.
+
+## Verification Plan
+
+### Automated Tests
+- Build the project with `meson setup build --prefix=/usr && ninja -C build`
+- Verify no compilation errors
+- Check that the plugin is installed to the correct directory
+
+### Manual Verification
+- Launch Elementary Code
+- Open a markdown file ([.md](file:///home/chuck/.gemini/antigravity/brain/b88974f6-b6d8-4497-a368-2ef66eb65ce1/task.md) extension)
+- Verify the preview toggle button appears in the toolbar
+- Click the button or press Ctrl+Shift+M to show the preview pane
+- Verify markdown is rendered correctly with:
+  - Headers (H1-H6)
+  - Bold and italic text
+  - Lists (ordered and unordered)
+  - Code blocks with syntax highlighting
+  - Links
+  - Images
+  - Blockquotes
+  - Tables
+- Edit the markdown and verify the preview updates in real-time
+- Verify the preview can be toggled on/off
+- Test with non-markdown files to ensure the button doesn't appear

plugins/markdown-preview/markdown-preview.plugin

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+[Plugin]
+Module=markdown-preview
+Loader=C
+IAge=2
+Name=Markdown Preview
+Description=Live preview of rendered Markdown files in a side-by-side view
+Icon=view-paged-symbolic
+Authors=Elementary Code Contributors
+Copyright=Copyright © 2026 Elementary Code Contributors
+Hidden=false