docs(pages): add TinyMind logo as site hero + sidebar

Add dark-theme logo (bg 27,27,29, light ink) as the home-page hero
image and just-the-docs sidebar logo. Replaces the XOR decision-surface
plot at the top of index.md; gallery still reachable via button.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: danmcleran

docs/_config.yml

@@ -1,6 +1,7 @@
 theme: just-the-docs
 title: TinyMind
 description: Header-only C++ template library for neural networks on embedded systems
+logo: "/assets/tinymind_logo.png"
 baseurl: "/tinymind"
 url: "https://danmcleran.github.io"
 aux_links:

docs/assets/tinymind_logo.png

@@ -4,6 +4,8 @@ layout: default
 nav_order: 1
 ---
 
+<img src="{{ site.baseurl }}/assets/tinymind_logo.png" alt="TinyMind logo" width="160" style="display:block;margin:0 auto 1rem;">
+
 # Machine Learning for Embedded Systems
 {: .fs-9 }
 
@@ -14,10 +16,6 @@ nav_order: 1
 [View on GitHub](https://github.com/danmcleran/tinymind){: .btn .fs-5 .mb-4 .mb-md-0 }
 [Example Gallery]({{ site.baseurl }}/gallery){: .btn .fs-5 .mb-4 .mb-md-0 }
 
-![int8 XOR decision surface]({{ site.baseurl }}/assets/plots/xor_decision_surface.png)
-
-*A PyTorch-trained XOR network running pure-integer int8 inference in TinyMind — see the [Example Gallery]({{ site.baseurl }}/gallery) for behavior graphs of every example (each writes a CSV + ships a matplotlib `plot.py`).*
-
 ---
 
 ## Why TinyMind?