Docs: Update build instructions

Document SDL3 as a required dependency and describe how to build the
project with kde-builder.

Also consolidate the repo-local config as kde-builder.yaml (without the
leading dot) so it is recognized consistently.

README.md

@@ -16,7 +16,7 @@ A unified game launcher for KDE Plasma 6, inspired by [KDE Apps Initiative issue
 - Last-played timestamp
 - Optional SteamGridDB cover fetching (requires API key)
 - Optional KRunner integration (if KF6Runner is available at build time)
-- Optional gamepad navigation (if Qt Gamepad is available at build time)
+- Gamepad navigation (via SDL3)
 
 ## Requirements
 
@@ -30,6 +30,7 @@ A unified game launcher for KDE Plasma 6, inspired by [KDE Apps Initiative issue
   - KCoreAddons
   - KConfig
 - Extra CMake Modules (ECM)
+- SDL3
 
 ### Runtime Dependencies
 
@@ -51,10 +52,36 @@ A unified game launcher for KDE Plasma 6, inspired by [KDE Apps Initiative issue
 
 ### Using kde-builder (Recommended)
 
+This project is not currently part of KDE's repo-metadata, so you need to add it as a custom project in your `~/.config/kde-builder.yaml`.
+
+1. Set up kde-builder:
+   - https://develop.kde.org/docs/getting-started/building/kde-builder-setup/
+2. Install distro build dependencies:
+
+```bash
+kde-builder --install-distro-packages
+```
+
+3. Add a project entry to `~/.config/kde-builder.yaml`:
+
+```yaml
+project alakarte:
+  repository: https://invent.kde.org/marcoa/a-la-karte.git
+  cmake-options: -DALAKARTE_SDL3_SOURCE_DIR=/path/to/SDL
+```
+
+4. Build:
+
 ```bash
 kde-builder alakarte
 ```
 
+To run the built app:
+
+```bash
+kde-builder --run alakarte
+```
+
 ### Manual Build
 
 ```bash

kde-builder.yaml

@@ -1,8 +1,10 @@
 # kde-builder configuration for A-La-Karte
 # See https://kde-builder.kde.org/en/configuration/config-file-overview.html
 
+config-version: 2
+
 global:
-  branch-group: kf6-qt6
+  branch-group: latest-kf6
   install-dir: ~/kde/usr
   source-dir: ~/kde/src
   build-dir: ~/kde/build
@@ -15,9 +17,8 @@ global:
   num-cores: auto
   num-cores-low-mem: 2
 
-  install-after-build: true
-
 project alakarte:
   repository: .
+  no-src: true
   cmake-options:
     - -DCMAKE_INSTALL_PREFIX=${install-dir}