docs: add Flatbread brand marks

assets/brand/README.md

@@ -0,0 +1,15 @@
+# Flatbread brand marks
+
+Each mark uses the same `0 0 1024 1024` view box, spacing, and tile geometry.
+
+- `flatbread-mark.svg` is the primary mark. Use it in the Flatbread README and
+  anywhere the dark plum tile fits.
+- `flatbread-mark-transparent.svg` keeps the full-color mark on a transparent
+  field. Use it on dark backgrounds.
+- `flatbread-mark-monochrome-dark.svg` is the one-color mark for light
+  backgrounds.
+- `flatbread-mark-monochrome-light.svg` is the one-color mark for dark
+  backgrounds.
+
+Keep the square view box and its clear space. Do not add shadows, gradients,
+text, or new colors to the marks.

packages/flatbread/README.md

@@ -1,8 +1,8 @@
 <p align="center">
-<img src="https://raw.githubusercontent.com/FlatbreadLabs/flatbread/main/assets/flatbread%20logo%20v2%20x4%401-1728x1080%20centered%20header.png"/>
+  <img src="https://raw.githubusercontent.com/FlatbreadLabs/flatbread/main/assets/brand/flatbread-mark.svg" alt="Flatbread logo" width="256" />
 </p>
 
-<h1 align="center">Flatbread 🥪</h1>
+<h1 align="center">Flatbread</h1>
 
 <p align="center">
   <a href="https://github.com/FlatbreadLabs/flatbread/actions/workflows/pipeline.yml">