Make openeo-test-suite WP3 process metadata tests pass

[zacdezgeo]

Context

PR #28 updated process JSON schemas and descriptions to improve OpenEO WP3 compliance.
However, when running the openeo-test-suite locally, several metadata-related tests still fail.
These failures are not blocking the PR, but should be addressed to ensure full WP3 compatibility.

Goal

Make the openeo-test-suite metadata tests pass (or explicitly document any intentional deviations).

Reproduction

Run the OpenEO test suite against a local titiler-openeo instance.

Example:

• Start titiler-openeo locally
• Run the openeo-test-suite metadata tests (see PR fix: validation openeo-test-suite WP3 #28 for the exact command and auth setup)

Acceptance Criteria

• src/openeo_test_suite/tests/processes/metadata passes against a local titiler-openeo instance
• Any skipped or unsupported tests are explicitly documented with rationale
• (Optional) Add short documentation on running the openeo-test-suite locally