build: drop the agent-specific gradle wrapper from the devshell

The flock/nice/worker-cap wrapper serialised local builds to protect the
shared box. That is now handled at the machine level (a GRADLE_OPTS cap
in nix-home), so the devshell goes back to the plain nix Gradle.

AGENTS.md

@@ -14,7 +14,6 @@ Everything comes from the Nix flake devshell; do not install toolchains by hand.
 - The default devshell provides JDK 21, Gradle 9, the Android SDK (platform 37, build-tools 37.0.0, platform-tools 37.0.1) and nushell.
 - The integration harness needs real servers, so it lives in a separate `nix develop .#integration` shell (navidrome, gonic, lms, php, Nextcloud with the Music app, sqlite). Keeping them out of the default shell avoids pulling that closure into everyday builds.
 - Build with the devshell `gradle`, not `./gradlew`. CI uses the nix Gradle pinned by `flake.lock`; the wrapper is kept only for people without Nix.
-- The devshell `gradle` is a wrapper: outside CI it takes a lock (under `$XDG_RUNTIME_DIR`, falling back to `~/.cache`) and runs under `nice` with a capped worker count, so several agents building at once queue instead of exhausting the box. `--stop`/`--status`/`--version` bypass the lock; with `CI` set it execs Gradle directly, unchanged.
 
 ## Commands
 

flake.nix

@@ -40,31 +40,9 @@
           };
           androidSdk = android.androidsdk;
 
-          gradle_wrapper = pkgs.writeShellScriptBin "gradle" ''
-            if [ -n "''${CI:-}" ]; then
-              exec ${pkgs.gradle_9}/bin/gradle "$@"
-            fi
-            for arg in "$@"; do
-              case "$arg" in
-                -v | --version | --status | --stop)
-                  exec ${pkgs.gradle_9}/bin/gradle "$@"
-                  ;;
-              esac
-            done
-            runtime_dir="''${XDG_RUNTIME_DIR:-''${HOME:-/tmp}/.cache}"
-            mkdir -p "$runtime_dir"
-            lock="$runtime_dir/subtracks-gradle.lock"
-            if ! ${pkgs.util-linux}/bin/flock -n "$lock" ${pkgs.coreutils}/bin/true 2>/dev/null; then
-              echo "gradle: waiting for the build lock at $lock" >&2
-            fi
-            export GRADLE_OPTS="''${GRADLE_OPTS:-} -Dorg.gradle.workers.max=4"
-            exec ${pkgs.util-linux}/bin/flock "$lock" \
-              ${pkgs.coreutils}/bin/nice -n 10 ${pkgs.gradle_9}/bin/gradle "$@"
-          '';
-
           basePackages = [
             pkgs.jdk21
-            gradle_wrapper
+            pkgs.gradle_9
             pkgs.git
             pkgs.curl
             pkgs.unzip