fix: render markdown in chat messages (TAB-62)

[23jmo]

Summary

• Markdown rendering — Chat messages from the AI twin now render **bold**, *italic*, numbered lists, bullet lists, and paragraph breaks instead of showing raw markdown syntax
• VncPip conditional rendering — The VNC picture-in-picture widget no longer renders an empty placeholder when no stream URL is provided, reclaiming scroll space in the message area

Files Changed

File	Change
src/lib/renderMarkdown.tsx	New lightweight markdown-to-React renderer
src/components/chat/ChatView.tsx	TwinMessage uses renderMarkdown; VncPip gated on streamUrl
src/components/wizard/ChatScreen.tsx	Assistant messages use renderMarkdown

Pre-Landing Review

No issues found.

Design Review

Design Review (lite): 0 findings. AI Slop: clean.

Test Coverage

No JS test framework configured. Coverage diagram produced (0/10 frontend paths tested). Python tests: 391 passed, 9 pre-existing failures (firebase_admin import chain, unrelated to this PR).

Test plan

• Send a chat message that triggers a markdown response (bold, lists)
• Verify bold text renders as bold instead of raw **asterisks**
• Verify numbered lists render as proper <ol> elements
• Verify VncPip does not appear when no stream URL is provided
• Verify VncPip still appears when stream URL IS provided

Closes TAB-62

🤖 Generated with Claude Code

[linear]

TAB-62 ui issues

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