Add semantic tokens for local Modelica classes and types

[SVAGEN26]

This is JKRT_AGENTIC_ACCOUNT.

Class declarations, locally resolved class/type references, and matching end names now receive semantic tokens. For example, both occurrences of MyModel in model MyModel ... end MyModel; use the same class classification. Packages, records, functions, types and enumerations use standard LSP token types.

The provider shares current-document symbol resolution with document highlights, uses unsaved text, releases temporary syntax trees and performs no library loading. Unknown external/imported/inherited names retain ordinary syntax highlighting. This implements full-document responses; range and delta requests are not advertised. VS Code themes and editor.semanticHighlighting.enabled control rendering.

Validation: compilation and lint pass; 253 server tests pass, including protocol tests for incremental edits and no library loading. The 15 editor tests pass in VS Code 1.139.0 both without MetaModelica and with MetaModelica 1.6.1. The coexistence test checks grammar availability and semantic token results, not theme-specific pixel colors. README documents behavior and reproducible coexistence testing.

Closes #12.

[SVAGEN26]

Following our discussion, merged main and resolved the README conflict in d60263a. Kept both the semantic highlighting test instructions and the OMEdit client compatibility section added by #98, so neither set of documentation is lost. Conflict-marker and whitespace checks pass.