fix: return undefined error type for non-Error values

[kashishhora]

Summary

Modified

• captureException now returns undefined type for non-Error objects (instead of "UnknownErrorType")
• unwrapErrorCauses returns undefined type for non-Error causes in error chains
• captureCallToolResultError returns undefined type when SDK converts errors to CallToolResult format

Fixed

• Updated test assertions to expect undefined instead of "UnknownErrorType" for non-Error values
• Updated SDK version-dependent tests to include undefined in valid type values

Test Plan

• All 253 tests pass
• TypeScript type checking passes
• ESLint passes