Improve error messages and API consistency across MCP functions

[johnkferguson]

Several functions have inconsistent error handling that makes debugging difficult:

Issues Found

1. search_symbols without version: Returns generic "HTTP error! status: 404" instead of indicating missing required parameter

2. Path format confusion: get_source_code and get_type_info use different path formats:

   • get_type_info works with: "prelude/fn.use_signal.html"
   • get_source_code expects: "ser/mod.rs" (but still fails)

3. Silent failures: get_crate_documentation returns a message but no indication of what went wrong

Suggested Improvements

1. Better error messages:

   • "Version parameter required for search_symbols"
   • "Invalid path format, expected: ..."
   • Specific reason for documentation retrieval failures

2. Consistent path formats:

   • Document expected path format for each function
   • Provide examples in error messages

3. Parameter validation:

   • Validate required parameters before making HTTP requests
   • Return clear validation errors

Additional Context

This would significantly improve the developer experience when the MCP functions don't work as expected.