Replace TypeScript with-arguments import planning

[tconley1428]

Summary

• replace the TypeScript-specific @nexus.typescript-with-arguments path with generic function type descriptors sourced from @nexus.function
• remove WithArgumentsFieldSpec / PlannedFieldRole::WithArguments planning and render typed argument overloads from function metadata instead
• carry generic import metadata on language string specs instead of precomputing imports in spec parsing
• move TypeScript and Python import inference into their language generators
• rename the TypeScript signal helper from converter-style signalFunctionToProto to name-extractor signalFunctionName

Generated output

• TypeScript generated output only renames the signal helper and call site
• No generated Python or .NET output changes

Tests

• cargo fmt
• cargo run -- build-examples
• cargo test