Delta GET /delta/v1/config ignores protocol-versions and never negotiates / rejects per spec

Describe the bug

GET /delta/v1/config ignores the protocol-versions query parameter and unconditionally returns "protocol-version": "1.0". DeltaApiService.getConfig on main:

// For now, we only have 1.0 as the first protocol version. Input protocolVersions is ignored.
return new DeltaCatalogConfig().endpoints(ENDPOINTS).protocolVersion("1.0");

But spec/protocols/ManagedTablesSpec.md (§ Get Configuration) and api/delta.yaml both define this endpoint as the protocol's version-negotiation bootstrap:

• protocol-versions is required: "Comma-separated list of the highest protocol versions the client supports per major version (e.g., "1.1,2.3" means the client supports 1.0-1.1 and 2.0-2.3)."
• "The server selects the highest mutually supported version and returns endpoints for that version."
• "If the client and server share no protocol version, the server rejects the request with InvalidParameterValueException (400) and an error message naming the protocol versions it supports. The client should treat this like an unsupported server."

None of that is enforced today. The server accepts a missing parameter, a malformed one, or a version it does not implement, and answers 200 / "1.0" in every case — so a client that only speaks a hypothetical 2.x would be told the server negotiated 1.0 and go on to call /v1/... endpoints with 2.x semantics, instead of getting the spec'd 400 and falling back.

To Reproduce

Against a server on main with a catalog unity:

$ curl -s "http://localhost:8080/api/2.1/unity-catalog/delta/v1/config?catalog=unity"
{"endpoints":[...],"protocol-version":"1.0"}          # expected 400: parameter is required

$ curl -s "http://localhost:8080/api/2.1/unity-catalog/delta/v1/config?catalog=unity&protocol-versions=2.0"
{"endpoints":[...],"protocol-version":"1.0"}          # expected 400 InvalidParameterValueException naming "1.0"

$ curl -s "http://localhost:8080/api/2.1/unity-catalog/delta/v1/config?catalog=unity&protocol-versions=garbage"
{"endpoints":[...],"protocol-version":"1.0"}          # expected 400

Expected behavior

Per the spec:

System [please complete the following information]:

• main at 958fded, also present in v0.5.0 / v0.5.1

Additional context

Only one protocol version (1.0) exists today, so this has no effect on current Delta clients — but that is exactly why it is cheap to get right now: enforcing the required parameter and the 400 path before a 1.1/2.0 ever ships means no client is ever built against the lenient behaviour. I have a fix + tests ready and will open a PR.

Start with DeltaApiService.getConfig and compare its handling of protocolVersions with § Get Configuration in spec/protocols/ManagedTablesSpec.md and api/delta.yaml. Verify the required, malformed, and unsupported-version cases described in the issue, including the successful 1.0 negotiation and the specified 400 responses. Done means validation and coverage match the documented behavior.