feat: render markdown images with click-to-enlarge lightbox

[dgrissen2]

Summary

Adds full ![alt](path) image rendering to the Viewer component. Previously, markdown image syntax was silently treated as plain text. Images now render inline with a click-to-enlarge lightbox overlay.

What's included

Image rendering

• ![alt](path) markdown syntax now renders as actual <img> elements
• Works in headings, paragraphs, list items, blockquotes, and table cells
• Remote URLs (https://...) render directly; local paths proxy through /api/image
• cursor-zoom-in on thumbnails hints they're interactive

Root cause of the silent failure

The InlineMarkdown special-character scanner (/[\*[]/)) did not include !, so had its!consumed as plain text, leavingaltto match as a regular link. Fixed by adding!` to the scan set and placing the image regex before the link regex.

Click-to-enlarge lightbox

• Click any image → full-screen dark overlay with image scaled to 90vw / 85vh
• Alt text shown as caption below
• Dismiss: Escape, backdrop click, or the cursor changes to zoom-out to make it obvious
• Portaled to document.body — same pattern as ImageAnnotator

Relative path resolution

Markdown files commonly reference images with relative paths (./images/chart.png). The server's process.cwd() is not necessarily the markdown file's directory, so these paths were 404ing.

Fix: getImageSrc() now accepts an optional base directory and appends ?base=<dir> to the API URL. handleImage in shared-handlers.ts falls back to resolving the path relative to base when the primary path doesn't exist. App.tsx captures filePath from the /api/plan response (already sent by the annotate server) and derives imageBaseDir to pass to <Viewer>.

Files changed

File	Change
packages/ui/components/Viewer.tsx	Image regex, imageBaseDir/onImageClick prop chain, ImageLightbox component
packages/ui/components/ImageThumbnail.tsx	getImageSrc(path, base?) optional base param
packages/editor/App.tsx	Capture filePath → derive imageBaseDir → pass to Viewer
packages/server/shared-handlers.ts	handleImage fallback resolution via ?base= query param

Test plan

• Open a markdown file with ![alt](https://...) — remote image renders
• Open a markdown file with ![alt](./relative/path.png) — local image renders
• Open a markdown file with ![alt](/absolute/path.png) — absolute path renders
• Click an image → lightbox opens with alt caption
• Press Escape → lightbox closes
• Click backdrop → lightbox closes
• Regular [link](url) still works (not accidentally matched as image)
• Inline image mid-paragraph renders without breaking surrounding text

🤖 Generated with Claude Code

[backnotprop]

Code review

No issues found. Checked for bugs and CLAUDE.md compliance.

🤖 Generated with Claude Code