feat: build dynamic AI chat stream previewer with simulated message ticks

[CHASE3020]

Closes #19

What changed

• New ChatMessage.tsx — dedicated message renderer with:

  • Markdown parsing: **bold**, `inline code`, fenced code blocks, unordered lists
  • Action card injection: detects [ACTION: APPROVE_TRANSFER: ...] markers and renders interactive Approve/Reject buttons with Framer Motion entrance animations
  • Streaming cursor: animated blinking cursor while the message is still streaming
  • Structured briefing widget: renders executive summary cards for financial data

• Rewritten NvidiaAssistantWidget.tsx — simulated streaming:

  • Word-by-word progressive rendering with realistic pacing (punctuation pauses, shorter words render faster)
  • Auto-scroll to bottom during streaming, respects manual scroll-up via scroll tracking
  • Timer cleanup on unmount to prevent memory leaks
  • Typing indicator shown only before the first assistant token arrives

• Updated types.ts — added isPartial flag and ActionCard interface

Verification

• npx tsc --noEmit — passes clean (noUncheckedIndexedAccess: true)
• npx next lint — no warnings or errors
• `npx prettier --check "src/features/chat/*.{ts,tsx}"" — all files formatted

Testing

1. Send a short prompt → text appears word-by-word with a blinking cursor
2. Send "balance" → action card with Approve/Reject buttons renders inline
3. Send "gas" → markdown list renders with bold values
4. Send any other text → standard streaming response
5. Scroll up during streaming → auto-scroll pauses; scroll to bottom resumes
6. Unmount the component mid-stream → no console errors (timers cleaned up)

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[mergekeeper]

MergeKeeper review

Scope: in scope for linked issue #19.
Verdict: clean

The pull request successfully implements the dynamic AI Assistant chat stream previewer with simulated message ticks, Markdown rendering, action card parsing, and auto-scroll handling as requested by issue #19.

Reviewed commit: ec7e679d387eb691a9f75e4589fad893448e92dc.
CI and merge eligibility are checked separately.

[mergekeeper]

Approved

The pull request successfully implements the dynamic AI Assistant chat stream previewer with simulated message ticks, Markdown rendering, action card parsing, and auto-scroll handling as requested by issue #19.

[mergekeeper]

MergeKeeper merge status

Status: blocked
PR state: open
Mergeability: mergeable
Checked commit: ec7e679d387eb691a9f75e4589fad893448e92dc.

Reason:
GitHub pull request merge request failed with 405: 3 of 3 required status checks are expected.

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