test: add unit tests for `lsp/`

[KRRT7]

Parent: #2079

Phase 1 — LSP module

Module	Stmts	Current coverage
lsp/	681	4%

Key files to cover:

• lsp/beta.py (326 stmts, 0%)
• lsp/lsp_message.py (78 stmts, 0%)
• lsp/server.py (51 stmts, 0%)
• lsp/helpers.py (47 stmts, 0%)
• lsp/features/perform_optimization.py (65 stmts, 0%)
• lsp/lsp_logger.py (105 stmts, 28%)

Mock LSP client connections and message transport. Test message parsing, server initialization, and feature dispatch.

Target

100% coverage for lsp/ (~681 statements).