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.
Concrete Log subclass for the engine debug log. Captures time, level,
and subsystem prefix per entry; stack-trace continuation lines attach
to the triggering ERROR entry via PatternParser's append-on-no-match
behaviour. Detectors: filename match on DebugLog-server.txt plus two
content signatures (the version=X.Y.Z+hash banner and the level/
subsystem/f/t/st header shape). Pattern constants live in
src/Pattern/ProjectZomboid/DebugServerPattern.php with named groups
ready for analyser use in phase B. Synthetic fixture under
test/src/Games/ProjectZomboid/fixtures/ uses zeroed identifiers and
placeholder paths.
