docs(readme): add logo to README header

Logo generated via Google Gemini 3.1 Flash Image Preview (nano-banana-2)
through a throwaway /tmp/vibe-resume-assets/gen.py script that reads the
API key from macOS keychain (service=generativelanguage.googleapis.com,
account=gemini-nano-banana-2) — not from an env var, per the global
CLAUDE.md rule against OS-level env var secrets.

Design: two-column academic preprint page + quill whose ink trail
becomes a neural-node graph in amber. Reads as "traditional academic
paper writing, AI-assisted" — matches vibe-sci's contract.

Source PNG: 1024x1024 PNG, ~1.2 MB. Render in README at width=180
(compact; browsers downscale cleanly). Raw asset kept in
assets/logo.png for reuse (favicon, social preview, etc.).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jeffhsu-chiuchau

README.md

@@ -1,3 +1,7 @@
+<p align="center">
+  <img src="assets/logo.png" width="180" alt="vibe-sci logo — an academic paper being written by a quill whose ink trails off into a neural network"/>
+</p>
+
 # vibe-sci
 
 Provider-neutral autonomous ML research paper writer — **ideation → LaTeX writeup → peer review → anti-hallucination numerical audit**.