fix(fastmcp): handle strings containing numbers correctly

This is a port of https://github.com/jlowin/fastmcp/pull/63 to this repo
- I guess the transition was made before this PR was merged into
fastmcp, so it wasn't included here.

See https://github.com/jlowin/fastmcp/issues/62 for the initial bug
report.

src/mcp/server/fastmcp/utilities/func_metadata.py

@@ -88,7 +88,7 @@ class FuncMetadata(BaseModel):
                     pre_parsed = json.loads(data[field_name])
                 except json.JSONDecodeError:
                     continue  # Not JSON - skip
-                if isinstance(pre_parsed, str):
+                if isinstance(pre_parsed, (str, int, float)):
                     # This is likely that the raw value is e.g. `"hello"` which we
                     # Should really be parsed as '"hello"' in Python - but if we parse
                     # it as JSON it'll turn into just 'hello'. So we skip it.