Add friend library comparison and game comments features

- CompareController: side-by-side library diff with stats (common games, rating diff)
- GameCommentController + GameCommentPolicy: threaded comments with replies, auth-gated
- GameComment model with top-level scope and self-referential replies relation
- Migration: game_comments table with parent_id for threading
- games/show: Discussion section with Alpine.js (post, reply, delete)
- compare/show: tabbed view (in common, they have, you have) with game cards
- users/show: "Compare Libraries" button visible to other authenticated users

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

app/Http/Controllers/CompareController.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\User;
+
+class CompareController extends Controller
+{
+    public function show(User $user)
+    {
+        if (auth()->id() === $user->id) {
+            return redirect()->route('users.show', $user->username);
+        }
+
+        $myGames    = auth()->user()->library()->with('game')->get()->keyBy('game_id');
+        $theirGames = $user->library()->with('game')->get()->keyBy('game_id');
+
+        $myIds    = $myGames->keys()->values();
+        $theirIds = $theirGames->keys()->values();
+
+        $bothIds          = $myIds->intersect($theirIds)->values();
+        $theyHaveNotYouIds = $theirIds->diff($myIds)->values();
+        $youHaveNotThemIds = $myIds->diff($theirIds)->values();
+
+        $both = $bothIds->map(fn($id) => [
+            'game'       => $myGames[$id]->game,
+            'myEntry'    => $myGames[$id],
+            'theirEntry' => $theirGames[$id],
+        ])->filter(fn($item) => $item['game'] !== null)->values();
+
+        $theyHaveNotYou = $theyHaveNotYouIds
+            ->map(fn($id) => $theirGames[$id])
+            ->filter(fn($ug) => $ug->game !== null)
+            ->values();
+
+        $youHaveNotThem = $youHaveNotThemIds
+            ->map(fn($id) => $myGames[$id])
+            ->filter(fn($ug) => $ug->game !== null)
+            ->values();
+
+        // Average rating diff on games both rated
+        $diffSum   = 0;
+        $diffCount = 0;
+        foreach ($bothIds as $id) {
+            $myRating    = $myGames[$id]->rating;
+            $theirRating = $theirGames[$id]->rating;
+            if ($myRating !== null && $theirRating !== null) {
+                $diffSum += abs($myRating - $theirRating);
+                $diffCount++;
+            }
+        }
+
+        $stats = [
+            'both_count'     => $bothIds->count(),
+            'they_not_you'   => $theyHaveNotYouIds->count(),
+            'you_not_them'   => $youHaveNotThemIds->count(),
+            'avg_rating_diff' => $diffCount > 0 ? round($diffSum / $diffCount, 1) : null,
+        ];
+
+        return view('compare.show', compact('user', 'both', 'theyHaveNotYou', 'youHaveNotThem', 'stats'));
+    }
+}

app/Http/Controllers/GameCommentController.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\Game;
+use App\Models\GameComment;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+class GameCommentController extends Controller
+{
+    public function store(Request $request, Game $game): JsonResponse
+    {
+        $data = $request->validate([
+            'body'      => 'required|string|max:1000',
+            'parent_id' => 'nullable|integer|exists:game_comments,id',
+        ]);
+
+        if (isset($data['parent_id'])) {
+            $parent = GameComment::findOrFail($data['parent_id']);
+            abort_if($parent->game_id !== $game->id, 422, 'Parent comment does not belong to this game.');
+        }
+
+        $comment = $game->comments()->create([
+            'user_id'   => auth()->id(),
+            'body'      => $data['body'],
+            'parent_id' => $data['parent_id'] ?? null,
+        ]);
+
+        $comment->load('user');
+
+        return response()->json([
+            'id'           => $comment->id,
+            'body'         => $comment->body,
+            'user'         => ['name' => $comment->user->name, 'username' => $comment->user->username],
+            'user_id'      => $comment->user_id,
+            'created_at'   => $comment->created_at->diffForHumans(),
+            'replies_count' => 0,
+        ], 201);
+    }
+
+    public function destroy(GameComment $comment): JsonResponse
+    {
+        $this->authorize('delete', $comment);
+        $comment->delete();
+
+        return response()->json(['deleted' => true]);
+    }
+}

app/Http/Controllers/GameController.php

@@ -3,6 +3,7 @@
 namespace App\Http\Controllers;
 
 use App\Models\Game;
+use App\Models\GameComment;
 use App\Models\Genre;
 use App\Models\Platform;
 use Illuminate\Http\Request;
@@ -54,7 +55,13 @@ class GameController extends Controller
             $userLists  = auth()->user()->lists()->get(['id', 'title']);
         }
 
-        $response = view('games.show', compact('game', 'userGame', 'userReview', 'userLists'));
+        $comments = $game->comments()->whereNull('parent_id')
+            ->with(['user', 'replies.user'])
+            ->latest()
+            ->limit(20)
+            ->get();
+
+        $response = view('games.show', compact('game', 'userGame', 'userReview', 'userLists', 'comments'));
         return auth()->check()
             ? $response
             : response($response)->header('Cache-Control', 'public, max-age=300');