chore: add pre-commit hook to auto-apply spotless formatting

Adds .githooks/pre-commit which runs `./gradlew spotlessApply` and
re-stages any reformatted files before each commit. Also adds an
`installGitHooks` Gradle task (run once after cloning) that sets
`core.hooksPath = .githooks` so git picks up the hook automatically.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: coopernetes

.githooks/pre-commit

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Auto-apply Spotless formatting before each commit.
+# Install once with: ./gradlew installGitHooks
+
+set -euo pipefail
+
+echo "[pre-commit] Running spotlessApply..."
+./gradlew spotlessApply --quiet
+
+# Re-stage any files that Spotless just reformatted so the formatted
+# versions are included in the commit (not the originals).
+git diff --name-only | xargs -r git add
+
+echo "[pre-commit] Spotless: OK"

build.gradle

@@ -26,6 +26,15 @@ allprojects {
 }
 
 
+tasks.register('installGitHooks') {
+    group = 'build setup'
+    description = 'Configures git to use the .githooks/ directory (run once after cloning).'
+    doLast {
+        ['git', 'config', 'core.hooksPath', '.githooks'].execute(null, rootDir).waitFor()
+        println 'Git hooks installed — .githooks/pre-commit will run spotlessApply before each commit.'
+    }
+}
+
 subprojects {
     apply plugin: 'com.diffplug.spotless'