feat(core): implement NavigateAction handler

[kitelev]

Summary

Implements NavigateAction handler for RDF-driven action execution:

• Navigate to asset by direct URI (extracts UUID, looks up file via findFileByUID)
• Navigate to first result of SPARQL SELECT query
• Handle ASK queries (navigate to current asset if query returns true)
• Works in both UI and headless (CLI) modes

Implementation Details

• Added fileSystem parameter (type IFileSystemMetadataProvider) to ActionInterpreter constructor
• Added resolveAssetUri() private method to extract UUID from URI and look up file path
• Handler supports:
  • Direct URIs like https://exocortex.my/assets/uuid
  • SPARQL SELECT queries (navigates to first result's subject)
  • SPARQL ASK queries (navigates to current asset if query returns true)

Test Plan

• Unit tests: 7 new tests covering all scenarios
• Build: No errors
• Lint: No new errors in changed files
• All existing tests pass

Test Coverage

Test Case	Status
Navigate to asset by direct URI	✅
Navigate to first result of SPARQL SELECT query	✅
Return error when SPARQL query returns no results	✅
Return error when asset not found for direct URI	✅
Work in headless (CLI) mode	✅
Handle ASK queries	✅
Extract UUID from URI correctly	✅

Closes #1407