Implement parser lifecycle management and enhance concurrency safety

[e-filchenko-bosh]

Description

Fixes stability issues in the Turtle/SAMM Language Server caused by unsafe native Tree-sitter lifecycle handling.

Changes include:

• Serialize access to shared native TSParser/TSTree state used by asynchronous LSP requests.
• Release parser, syntax-tree, rope, and validation state when documents are closed or the service shuts down.
• Make document-service and validation cleanup idempotent.
• Add default ERROR-level diagnostics for samm lsp without enabling verbose logging for unrelated CLI commands.
• Add lifecycle and concurrency regression tests.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works

[atextor]

LGTM!