Port Go server/subject_transform.go to .NET. Implements a compiled
transform engine that parses source patterns with wildcards and
destination templates with function tokens at Create() time, then
evaluates them efficiently at Apply() time without runtime regex.
Supports all 9 transform functions: wildcard/$N, partition (FNV-1a),
split, splitFromLeft, splitFromRight, sliceFromLeft, sliceFromRight,
left, and right. Used for stream mirroring, account imports/exports,
and subject routing.
Move max payload validation from the parser to ProcessPubAsync so the
server sends -ERR 'Maximum Payload Violation' and closes the connection
(matching Go reference client.go:2442). In pedantic mode, reject PUB
with wildcard subjects via -ERR 'Invalid Publish Subject' (client.go:2869).
Add disposed guard to SubList.Remove to prevent crash during shutdown.
