Rationale

Markdown tables in the TUI could render as visually broken output when cells contained long titles, links, or HTML line breaks. Adjacent Ink text nodes wrapped independently, which let cells collide (for example, dates glued into paper titles), and optimistic body widths could produce right-edge truncation artifacts.

Summary

• Render Markdown tables as fixed-width bordered tables with pre-wrapped cell rows.
• Normalize table cell text by stripping inline Markdown for layout and replacing <br> with spaces.
• Keep table borders white while leaving table cell content at the default terminal text color; header rows remain bold.
• Pass measured body width through streaming and non-streaming Markdown render paths.

Test Plan

• npm test -- --run src/__tests__/markdown.test.ts
• npm run type-check
• npm run build
• npm exec prettier -- --check src/components/markdown.tsx src/__tests__/markdown.test.ts src/components/messageLine.tsx src/components/streamingMarkdown.tsx
• git diff --check

Note: full npm run lint still reports pre-existing errors outside this change; the changed files only had padding warnings before local cleanup.