Commit the Projects/Tasks/Ideas/TaskComments feature

This was already implemented, migrated, and running live, but had
never been committed. Bringing it into git: Project/Task/Idea/
TaskComment models, their JSON API (CRUD + status transitions,
task comments, idea<->project linking), Livewire UI pages, and the
nav/route wiring for them. All 42 of its own tests pass.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/Models/TaskComment.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\SoftDeletes;
+
+class TaskComment extends Model
+{
+    use HasFactory, SoftDeletes;
+
+    public const AUTHOR_TYPES = ['user', 'ai', 'system'];
+
+    protected $fillable = [
+        'task_id',
+        'body',
+        'author_type',
+        'author_name',
+    ];
+
+    public function task(): BelongsTo
+    {
+        return $this->belongsTo(Task::class);
+    }
+
+    public function isFromAI(): bool
+    {
+        return $this->author_type === 'ai';
+    }
+
+    public function isFromUser(): bool
+    {
+        return $this->author_type === 'user';
+    }
+
+    public function isSystem(): bool
+    {
+        return $this->author_type === 'system';
+    }
+}