fix: Add schema-aware numeric coercion for MCP tool arguments

[tlongwell-block]

Some LLMs quote numeric arguments when calling MCP tools (e.g., sending "42" instead of 42), which can cause tool execution failures. This change adds schema-aware coercion that automatically converts string representations of numbers to their proper numeric types, but only when the tool's schema explicitly indicates a parameter should be numeric. The implementation is conservative - if no schema is available, no coercion is performed to avoid accidentally modifying strings that should remain as strings.