Implement signature help for R function calls

[Copilot]

• Identify merge conflicts between signature help branch and main
• Resolve conflicts in lib.rs to include both signature_help and symbols modules
• Resolve conflicts in server.rs to merge imports and functionality from both branches
• Fix compilation error in signature help where Item.kind should be Item.info
• Update signature help to check for ItemInfo::Function instead of SymbolKind::FUNCTION
• Remove unused imports to eliminate warnings
• Verify all tests pass (78 total tests including 8 signature help tests)
• Complete merge with main branch successfully

The merge conflicts have been successfully resolved! The signature help functionality is now fully compatible with the latest changes from the main branch, including the new symbols module. All existing and new tests are passing.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[felix-andreas]

@copilot please fix conflicts

[Copilot]

@copilot please fix conflicts

Merge conflicts have been resolved! The signature help feature is now fully compatible with the latest main branch changes. Fixed conflicts in lib.rs and server.rs, and updated the signature help implementation to work with the new ItemInfo structure. All 78 tests are passing, including the 8 signature help tests.

Commit: 0dfa471