[Cosmos] [Embedding V0] _resolve_embeddings helper on hybrid-search aggregator (sync + async)

# Embedding-resolution helper on the hybrid-search aggregator (sync + async)

Parent: 46729
Depends on: 46730, 46731

## Goal

Add a single helper that takes the `embeddingParameterMap` from the plan, calls the customer-provided generator once with the full batch, and returns the augmented parameter list. No mutation of caller state.

## Scope

Add (sync) on `_HybridSearchContextAggregator`:

```python
def _resolve_embeddings(self):
embedding_map = self._partitioned_query_ex_info.get_embedding_parameter_map()
if not embedding_map:
return
generator = self._options.get("embeddingGenerator")
if generator is None:
raise ValueError(
"Query requires embedding generation but no embedding_generator "
"was passed to query_items."
)
keys, texts = zip(*sorted(embedding_map.items())) # stable order
vectors = generator.generate_embeddings(list(texts))
if len(vectors) != len(texts):
raise ValueError(
f"embedding_generator returned {len(vectors)} vectors for {len(texts)} texts"
)
for i, v in enumerate(vectors):
if v is None:
raise ValueError(f"embedding_generator returned a null vector at index {i}")
extra = [{"name": k, "value": list(v)} for k, v in zip(keys, vectors)]
base = list(self._parameters or [])
self._parameters = base + extra
```

Mirror in `aio/hybrid_search_aggregator.py`:

```python
async def _resolve_embeddings_async(self):
...
vectors = await generator.generate_embeddings_async(list(texts))
...
```

Add a type guard at the async entry point: if a sync `EmbeddingGenerator` is passed (no `generate_embeddings_async`), raise `TypeError` early with an actionable message.

## Non-goals

- Do NOT yet call this from `_run_hybrid_search`; that lives in 46733.
- Do NOT add the diagnostics span here; that lives in 46734 (but the call-site for the span will be inside this helper).

## Files touched

- `sdk/cosmos/azure-cosmos/azure/cosmos/_execution_context/hybrid_search_aggregator.py`
- `sdk/cosmos/azure-cosmos/azure/cosmos/_execution_context/aio/hybrid_search_aggregator.py`

## Acceptance

- Helper is non-mutating for the no-op case (no map → no parameter changes).
- Sort-stable (same map → same parameter order).
- Raises `ValueError` with clear messages on cardinality mismatch / null entry / missing generator.
- Async path raises `TypeError` if a sync generator is passed.
- 100 % unit-test coverage of the helper (covered by 46735).

Beginne mit sdk/cosmos/azure-cosmos/azure/cosmos/_execution_context/hybrid_search_aggregator.py und seinem asynchronen Gegenstück in aio/hybrid_search_aggregator.py. Lies den bestehenden Aggregator-Zustand und die Einstiegspunkte, bevor du die synchronen und asynchronen Hilfsfunktionen einschließlich des Guards für den asynchronen Generator hinzufügst. Erledigt bedeutet eine stabile, nicht mutierende Parameterauflösung mit den angegebenen Fehlern, abgedeckt durch die Unit-Tests in issue 46735.

Vom Indexierungsmodell aus dem Issue-Text verfasst.