Markdown tables (and other GFM extensions) render as raw text in PR detail view

[mayfieldiv]

Problem

Markdown tables in PR descriptions render as a blob of plain text with pipe characters instead of a formatted table. This is because mdast-util-from-markdown only supports CommonMark by default — GFM (GitHub Flavored Markdown) features like tables require additional extensions.

Example input:

| File | Change |
|------|--------|
| `cli/Cargo.toml` | Explicit tokio features |
| `cli/Cargo.lock` | Removed unused `parking_lot` dep |

Current rendering: a single paragraph containing the raw | File | Change | ... text, pipes and all.

Expected: a nicely formatted table with aligned columns and borders.

Root Cause

1. No GFM parser extensions — the project only has mdast-util-from-markdown (CommonMark). Tables, task lists, strikethrough, and autolinks all require micromark-extension-gfm + mdast-util-gfm to parse into proper AST nodes.
2. No table renderer — src/lib/markdown.tsx has no Match case for type === "table" / tableRow / tableCell, so even if parsed, tables would hit the FallbackBlock and render nothing.

Other GFM features affected

These are also commonly used in GitHub PR bodies and are similarly broken:

Feature	Syntax	Current behavior
Task lists	- [x] done	Renders as [x] done text
Strikethrough	~~deleted~~	Renders as ~~deleted~~ text
Autolinks	https://example.com	Plain text (no link)

Proposed Fix

1. Add GFM parsing extensions

bun add micromark-extension-gfm mdast-util-gfm

Then in src/lib/markdown.tsx:

import { gfm } from "micromark-extension-gfm";
import { gfmFromMarkdown } from "mdast-util-gfm";

// in MarkdownBody:
const tree = () => fromMarkdown(props.source, {
  extensions: [gfm()],
  mdastExtensions: [gfmFromMarkdown()],
});

2. Add table renderer component

Render table → tableRow → tableCell AST nodes as a TUI table. Key considerations:

• Column width calculation — measure the text content of each column across all rows, then pad to the max width per column
• Box-drawing borders — use ─, │, ┌, ┬, ┐, etc. for clean TUI table borders
• Alignment — the Table node has an align array ("left" | "center" | "right" | null) per column
• Header row — first tableRow is the header; render bold or with a separator line beneath
• Inline content in cells — cells contain PhrasingContent[], so reuse InlineNodes for rendering

3. (Bonus) Task lists, strikethrough

• Task lists: check listItem.checked (boolean | null) and render [✓] / [ ] prefix
• Strikethrough: wrap in ~~ style (dim or strikethrough if terminal supports it)

Files to Modify

• package.json — add micromark-extension-gfm + mdast-util-gfm
• src/lib/markdown.tsx — wire up GFM extensions, add MdTable/MdTableRow/MdTableCell components, add task list + strikethrough support