Add ProjectZomboidChatLog (chat.txt)

Handles both chat-engine events (bracketed level prefix) and bare
server-alert lines via an optional level group. Detectors: filename
match on _chat.txt plus content signatures for ChatMessage{...} log
entries and the chat-server initialization banner. CHAT_MESSAGE and
SERVER_ALERT named-group regexes ride along on ChatPattern for analyser
extraction in phase B.

src/Pattern/ProjectZomboid/ChatPattern.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace IndifferentKetchup\Codex\Pattern\ProjectZomboid;
+
+/**
+ * Regex constants for the Project Zomboid chat.txt format.
+ *
+ * Two row variants share the file: bracket-level chat-engine events
+ * (e.g. [time][info] message) and bare server-alert messages
+ * (e.g. [time] Server alert ...). The LINE pattern accepts both via an
+ * optional non-capturing wrapper around the level.
+ *
+ * LINE captures, in order:
+ *   1. time  (DD-MM-YY HH:MM:SS.mmm)
+ *   2. level (info | warn | error | empty for server alerts)
+ */
+class ChatPattern
+{
+    public const string LINE = '/^\[(\d{2}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}\.\d{3})\](?:\[(\w+)\])?\s+.*$/';
+
+    public const string CHAT_MESSAGE = '/ChatMessage\{chat=(?<channel>\w+), author=\'(?<author>[^\']+)\', text=\'(?<text>.*?)\'\}/';
+
+    public const string SERVER_ALERT = '/^Server alert message:\s*\'(?<text>.*?)\'\s+sent\.\.?$/';
+}