Cosmos: Support binary vector queries

### Feature Summary

Add Cosmos binary encoding support for vector search query responses.

### Feature Description

After the cross-partition vector query work in #5130 and the current binary query work in #5040 and #5070 merge, extend binary response handling to vector search queries, including the non-streaming ordered merge path used by `ORDER BY VectorDistance(...)`.

The implementation should preserve the existing binary negotiation and text-fallback contract, decode service-provided sort-key envelopes without lossy text coercion, and emit merged results in the negotiated response format.

Acceptance criteria:

- Binary responses work for single- and cross-partition vector queries.
- Indexed and brute-force `VectorDistance` queries are supported.
- Finite `TOP` and `OFFSET`/`LIMIT` windows work through the non-streaming ordered merge path.
- Filters and bound vector parameters behave consistently in binary and text modes.
- Text fallback remains supported when the service cannot return binary.
- Tests cover CosmosBinary, JsonText, and fallback behavior without changing default behavior when binary encoding is disabled.

### Use Case

Reduce vector-query response size and preserve binary numeric fidelity while supporting global cross-partition vector ranking.

### Alternatives

Continue using text JSON for vector query responses, which forfeits binary encoding's size and numeric-fidelity benefits.

### Additional Context

Parent epic: #4823

Depends on #5130 and should be implemented after the active query encoding work in #5040 and #5070 lands.

Start by reviewing the cross-partition vector query work in #5130 and the binary query work in #5040 and #5070. Trace Cosmos binary response handling and the non-streaming ordered merge path for ORDER BY VectorDistance(...). Done means single- and cross-partition indexed and brute-force queries support binary responses, text fallback, filters, bound vectors, and the listed windows with coverage for CosmosBinary and JsonText.

Written by the indexing model from the issue text.