inlay hints for types and parameter names

[michaeldistel]

Summary

Implement textDocument/inlayHint to show inline type annotations for var declarations and parameter names at call sites.

Scope

• Parameter name hints at positional FB/function call sites (e.g. IN:)
• Type hints for VAR declarations without explicit type (if inferred)
• Toggleable via VS Code inlay hint settings

Implementation Notes

• New InlayHintsProvider in src/server/providers/
• Resolve parameter names from function/FB signatures via workspace indexer and iec61131-definitions/
• Register inlayHintProvider capability in server.ts

Acceptance

• Positional FB call shows parameter name hints
• Hints disappear when named-parameter syntax already used
• Toggled by editor.inlayHints.enabled
• Tests cover standard FB and custom FB call sites