type hierarchy (supertypes/subtypes)

[michaeldistel]

Summary

Implement textDocument/prepareTypeHierarchy and typeHierarchy/supertypes / typeHierarchy/subtypes to navigate TYPE inheritance chains.

Scope

• EXTENDS relationships between FUNCTION_BLOCKs
• TYPE alias chains
• Subtypes: all FBs that extend the selected FB
• Supertypes: chain of base FBs

Implementation Notes

• New TypeHierarchyProvider in src/server/providers/
• Requires workspace indexer to track EXTENDS declarations
• Register capability in server.ts

Acceptance

• Right-click → Show Type Hierarchy on a FUNCTION_BLOCK shows supertypes and subtypes
• Works cross-file
• Tests cover single-level and multi-level inheritance