feat: apply mission-control theme to docs site

Configure slate scheme with custom palette, IBM Plex Sans / JetBrains
Mono fonts, Syne for headings via template override, and wire up the
custom stylesheet.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: baijum

mkdocs.yml

@@ -6,6 +6,7 @@ repo_name: towlion/platform
 
 theme:
   name: material
+  custom_dir: overrides
   features:
     - navigation.tabs
     - navigation.sections
@@ -15,18 +16,15 @@ theme:
     - content.tabs.link
     - content.code.copy
   palette:
-    - scheme: default
-      primary: indigo
-      accent: indigo
-      toggle:
-        icon: material/brightness-7
-        name: Switch to dark mode
-    - scheme: slate
-      primary: indigo
-      accent: indigo
-      toggle:
-        icon: material/brightness-4
-        name: Switch to light mode
+    scheme: slate
+    primary: custom
+    accent: custom
+  font:
+    text: IBM Plex Sans
+    code: JetBrains Mono
+
+extra_css:
+  - stylesheets/custom.css
 
 nav:
   - Home: index.md

overrides/main.html

@@ -0,0 +1,18 @@
+{% extends "base.html" %}
+
+{% block extrahead %}
+  <link rel="preconnect" href="https://fonts.googleapis.com">
+  <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
+  <link href="https://fonts.googleapis.com/css2?family=Syne:wght@400;600;700;800&display=swap" rel="stylesheet">
+  <style>
+    .md-typeset h1,
+    .md-typeset h2,
+    .md-typeset h3,
+    .md-typeset h4,
+    .md-typeset h5,
+    .md-typeset h6 {
+      font-family: "Syne", sans-serif;
+      font-weight: 700;
+    }
+  </style>
+{% endblock %}