refactor: simplify output structure for altitude and WFS describe type tools

[esgn]

Closes #86

This PR removes the redundant result wrapper from singleton MCP tool outputs so their domain fields are exposed directly in structuredContent and in the serialized JSON text payload.

The change is intentionally limited to singleton object responses:

• altitude now returns { lon, lat, altitude, accuracy }
• gpf_wfs_describe_type now returns { id, namespace, name, title, description, properties }

The corresponding outputSchema definitions were flattened to match the new top-level shape, and the unit/integration tests were updated accordingly. List-style outputs using results are unchanged, and WFS FeatureCollection responses are explicitly out of scope.

This is an API cleanup and consistency change aligned with MCP output schema examples. It is a breaking response-shape change for any client currently reading structuredContent.result.