feat(server): add TCL signature help support

Adds a signature help system for TCL commands.
The LSP server now exposes signature help for custom and
built-in MOM procedures, enabling parameter hints while editing.
Tests and documentation were added to cover common usage.

- Adds signature_help module to parse and present signatures
- Integrates with LSP server to provide signature help on the client
- Adds tests for custom and built-in procedures

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Unreleased
+
+- Add signature help for custom TCL procedures and built-in NX/MOM procedures
+
 ## [0.0.1]
 
 - Initial release