[DOC] `Collection.add` / `query` docstrings list ValueErrors the client never raises

The `Raises:` sections of `Collection.add` and `Collection.query` (and the same text in `AsyncCollection`) describe three errors that chromadb 1.5.9 does not raise. The generated reference page `reference/python/collection.mdx` repeats them, and in two of the three cases the user guide already says the opposite.

| Docstring says | What happens (1.5.9) | Guide says |
|---|---|---|
| `add`: "ValueError: If an ID already exists." | No error. The existing record is kept and the new one is dropped. | `add-data.mdx:182`: "it will be ignored without throwing an error" |
| `add`: "ValueError: If embeddings and documents are both provided." | Accepted, both stored. `types.py` explicitly allows documents alongside embeddings. | `add-data.mdx:57`, `:60`: pass both, stored as-is |
| `query`: "ValueError: If multiple query input types are provided." | No error. With `query_embeddings` and `query_texts` both given, the embeddings are used and the texts are ignored. | — |

All three reproduce with `EphemeralClient` and with `HttpClient` against `chroma run`. The existing-ID `add` and the `query` case also reproduce with `AsyncHttpClient`.

## Reproduction

```python
import chromadb

col = chromadb.EphemeralClient().create_collection("repro", embedding_function=None)
e = [[0.1, 0.2, 0.3]]

col.add(ids=["a"], embeddings=e, documents=["first"])
col.add(ids=["a"], embeddings=[[0.9, 0.9, 0.9]], documents=["second"]) # documented to raise
print(col.get(ids=["a"])["documents"]) # ['first']

col.add(ids=["b"], embeddings=e, documents=["doc"]) # documented to raise; accepted

print(col.query(query_embeddings=e, query_texts=["unrelated"], n_results=1)["ids"]) # documented to raise; texts ignored
```

## Where

- `chromadb/api/models/Collection.py`: `add` Raises (lines 122, 124 on `main`), `query` Raises (268)
- `chromadb/api/models/AsyncCollection.py`: `add` Raises (84-85), `query` Raises (249-251)
- `docs/mintlify/reference/python/collection.mdx`: generated from the above by `docs/scripts/generate_python_reference.py`

## Versions

chromadb 1.5.9 (latest on PyPI), Python 3.11.6, Windows 11. Line numbers are from `main` at a7920e9.

## Proposed fix

For `add`, the behaviour matches the guide, so only the docstrings are wrong: drop the two lines, and state that an existing ID is ignored, pointing at `upsert`/`update`. Then regenerate `collection.mdx`.

`query` is less clear-cut. Silently ignoring `query_texts` when embeddings are also passed is easy to miss, so it could be either a docstring fix or a real check. Raising now would break callers that pass both today. Which would you prefer?

I can open a PR for the docstring changes.

Read the Raises sections in chromadb/api/models/Collection.py and chromadb/api/models/AsyncCollection.py, then run the EphemeralClient reproduction from the issue to confirm the documented behavior. Update the relevant docstrings and regenerate docs/mintlify/reference/python/collection.mdx with docs/scripts/generate_python_reference.py; done means the reference matches the supported behavior and the unresolved query case has an explicit decision.

Written by the indexing model from the issue text.