cover lms and nextcloud music in the integration suite

Run the integration harness from its own devshell so the server packages stay out of the everyday shell. Add lms and a Nextcloud Music instance to the harness and extend the suite with auth-fallback, media, error, write round-trip, multi-source and prune tests.

The auth test caught that lms answers OpenSubsonic error 42 (not 41) when it refuses token auth, so the client now falls back on both codes.

flake.nix

@@ -3,10 +3,18 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    # The integration shell runs real servers; pin them to a stable release. lms 3.80 (the
+    # version in unstable) segfaults at startup with wt 4.14.3, so the server packages come from
+    # here instead. The default shell never touches this input.
+    nixpkgs-stable.url = "github:NixOS/nixpkgs/nixos-26.05";
   };
 
   outputs =
-    { nixpkgs, ... }:
+    {
+      nixpkgs,
+      nixpkgs-stable,
+      ...
+    }:
     let
       systems = [ "x86_64-linux" ];
       forEachSystem = nixpkgs.lib.genAttrs systems;
@@ -22,6 +30,7 @@
               allowUnfree = true;
             };
           };
+          servers = import nixpkgs-stable { inherit system; };
           android = pkgs.androidenv.composeAndroidPackages {
             platformVersions = [ "37" ];
             buildToolsVersions = [ "37.0.0" ];
@@ -33,30 +42,51 @@
             includeCmake = false;
           };
           androidSdk = android.androidsdk;
+
+          basePackages = [
+            pkgs.jdk21
+            pkgs.gradle_9
+            pkgs.git
+            pkgs.curl
+            pkgs.unzip
+            pkgs.nushell
+            androidSdk
+            android.platform-tools
+          ];
+
+          shellHook = ''
+            echo "subtracks dev shell"
+            echo "  java:        $(java -version 2>&1 | head -n1)"
+            echo "  ANDROID_HOME: $ANDROID_HOME"
+          '';
         in
         {
           default = pkgs.mkShell {
-            packages = [
-              pkgs.jdk21
-              pkgs.gradle_9
-              pkgs.git
-              pkgs.curl
-              pkgs.unzip
-              pkgs.nushell
-              pkgs.navidrome
-              pkgs.gonic
-              androidSdk
-              android.platform-tools
-            ];
+            packages = basePackages;
 
             ANDROID_HOME = "${androidSdk}/libexec/android-sdk";
             ANDROID_SDK_ROOT = "${androidSdk}/libexec/android-sdk";
 
-            shellHook = ''
-              echo "subtracks dev shell"
-              echo "  java:        $(java -version 2>&1 | head -n1)"
-              echo "  ANDROID_HOME: $ANDROID_HOME"
-            '';
+            inherit shellHook;
+          };
+
+          # The integration harness starts real Subsonic servers, none of which the app build or
+          # unit tests need. Kept out of the default shell so those stay free of the server deps.
+          integration = pkgs.mkShell {
+            packages = basePackages ++ [
+              servers.navidrome
+              servers.gonic
+              servers.lms
+              servers.sqlite
+              servers.php83
+            ];
+
+            ANDROID_HOME = "${androidSdk}/libexec/android-sdk";
+            ANDROID_SDK_ROOT = "${androidSdk}/libexec/android-sdk";
+            NEXTCLOUD_DIR = "${servers.nextcloud34}";
+            NEXTCLOUD_MUSIC_APP = "${servers.nextcloud34Packages.apps.music}";
+
+            inherit shellHook;
           };
         }
       );