feat: give the app icon a mark that inverts with the colour scheme

CHANGELOG.md

@@ -30,6 +30,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   price, the readout stays absent rather than quoting a total that is missing a
   turn.
 
+### Changed
+
+- **New app icon.** The purple flame is now a monochrome one that inverts with
+  the colour scheme: white on dark, black on light. The window and tab icon
+  follows the scheme live; the launcher, dock and taskbar icon is a single
+  image the desktop cannot re-theme, so it ships white.
+
 ### Fixed
 
 - **Settings › Font lists your installed fonts on Windows.** The picker read the

README.md

@@ -1,5 +1,8 @@
 <div align="center">
-  <img src="frontend/public/appicon.png" alt="lich" width="88" height="88" />
+  <picture>
+    <source media="(prefers-color-scheme: dark)" srcset="frontend/public/appicon.png" />
+    <img src="frontend/public/appicon-light.png" alt="lich" width="88" height="88" />
+  </picture>
   <h1>lich</h1>
   <p><strong>A terminal-first harness for coding with AI agents.</strong></p>
   <p>

frontend/index.html

@@ -3,7 +3,8 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover" />
-    <link rel="icon" type="image/png" href="/appicon.png" />
+    <!-- SVG so the mark can invert with the scheme; Chrome ignores `media` on a PNG icon link. -->
+    <link rel="icon" type="image/svg+xml" href="/appicon.svg" />
     <title>lich</title>
   </head>
   <body>