Record why the Android NDK is required

Hiding the NDK and rebuilding showed the build fails without it, and the reason
is not obvious from this repository: maplibre_gl pins ndkVersion 28.2.13676358
in its own build file, and AGP needs every module to agree on one NDK. The app
has no native sources and no Dart FFI, so the declaration reads like dead
configuration and invites exactly the deletion that was just tried.

Costs about 2 GB of Android SDK. Notes the full toolchain disk budget in the
README as well, since a warm Gradle cache plus build output pushes the total to
roughly 14 GB.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Nuvolari/README.md

@@ -30,6 +30,11 @@ Start with [docs/architecture.md](docs/architecture.md), then
 | Android SDK | platform 36, build-tools 36.0.0, platform-tools |
 | JDK | 21 |
 | Python | 3.12+ (3.14 works; rasterio ships wheels for it) |
+| Android NDK | 28.2.13676358 — pinned by `maplibre_gl`, not by this project |
+
+A full toolchain plus a warm Gradle cache needs roughly **14 GB** of disk: Flutter
+3 GB, Android SDK 2.5 GB (2 GB of which is the NDK the map plugin pins), the Gradle
+cache 5 GB, and build output around 2 GB. `flutter clean` reclaims the last of those.
 
 ## Configuration