Preserve signed arguments after custom argument parse failures

[neonjava]

Fixes #14076

When a custom argument parser fails before a signed message argument, Paper may parse fewer signed arguments than the client sent. The signature check then rejects the command and breaks the player's chat chain.

If the custom parse fails, parse the command again using the argument types sent to the client for signature checking. Keep the original parse result for command execution.

Tested on Paper 26.3 with a custom argument that fails before a signed message: the original build reported an argument signature mismatch and rejected the next chat message; this build reports the command parse error and accepts the next chat message. The regression test and :paper-server:compileJava pass.