fix(python): accept VoyageAI text batch containers (#4558)

Direct VoyageAI `compute_source_embeddings()` calls reject `list[str]`
and NumPy text batches before reaching the provider, although both
belong to the declared `TEXT` input type. For example, `["first",
"second"]` raises `ValueError: Input type <class 'list'> not allowed
with text model.`

Normalize these containers to a list before the existing string-entry
validation. The regression cases exercise the public embedding API with
a stub provider: input order, list/NumPy batches, Arrow controls, empty
batches, and rejection of non-text entries and ordinary two-dimensional
arrays. The VoyageAI integration page now documents the accepted text
containers.

Verified on current main `7b3ba4c` with a locally compiled native
extension (0.41.0b7, Python 3.12.12):

- VoyageAI suite: 7 failed / 20 passed before the fix; 27 passed
afterward.
- Adjacent embedding suite: 13 passed, 4 skipped, 8 slow cases
deselected.
- Python CI's pinned Ruff 0.9.9 lint/format checks pass; configured
Pyright reports zero errors/warnings; all applicable pre-commit hooks
pass.

The provider is stubbed; no live Voyage API request or model-quality
evaluation was performed.

AI disclosure: I used Codex for investigation, implementation, tests,
review, and drafting this description.

docs/web/integrations/embedding/voyageai.mdx

@@ -45,6 +45,8 @@ Supported parameters (to be passed in `create` method) are:
 | `output_dimension` | `int` | `None` | Output embedding dimension. Only supported by `voyage-multimodal-3.5`. Valid options: 256, 512, 1024 (default), 2048. |
 
 
+For text models, `compute_source_embeddings()` accepts a single string, a list of strings, a one-dimensional NumPy array, or a PyArrow `Array` or `ChunkedArray`. Batch inputs retain their order.
+
 Usage Example:
 
 <CodeGroup>
@@ -61,4 +63,4 @@ The `voyage-multimodal-3.5` model can embed text alongside images. You can use i
   <CodeBlock filename="Python" language="Python" icon="python">
     {PyEmbeddingVoyageaiMultimodal}
   </CodeBlock>
-</CodeGroup>
+</CodeGroup>