feat(tests): introduce a test "suite" concept to encompass dirs, options (#3339)

Our integration tests need to be 'grouped' because each group often
needs a specific set of models it works with. We separated vision tests
due to this, and we have a separate set of tests which test "Responses"
API.

This PR makes this system a bit more official so it is very easy to
target these groups and apply all testing infrastructure towards all the
groups (for example, record-replay) uniformly.

There are three suites declared:
- base
- vision
- responses

Note that our CI currently runs the "base" and "vision" suites.

You can use the `--suite` option when running pytest (or any of the
testing scripts or workflows.) For example:
```
OLLAMA_URL=http://localhost:11434 \
  pytest -s -v tests/integration/ --stack-config starter --suite vision
```

tests/integration/README.md

@@ -42,6 +42,27 @@ Model parameters can be influenced by the following options:
 Each of these are comma-separated lists and can be used to generate multiple parameter combinations. Note that tests will be skipped
 if no model is specified.
 
+### Suites (fast selection + sane defaults)
+
+- `--suite`: comma-separated list of named suites that both narrow which tests are collected and prefill common model options (unless you pass them explicitly).
+- Available suites:
+  - `responses`: collects tests under `tests/integration/responses`; this is a separate suite because it needs a strong tool-calling model.
+  - `vision`: collects only `tests/integration/inference/test_vision_inference.py`; defaults `--vision-model=ollama/llama3.2-vision:11b`, `--embedding-model=sentence-transformers/all-MiniLM-L6-v2`.
+- Explicit flags always win. For example, `--suite=responses --text-model=<X>` overrides the suite’s text model.
+
+Examples:
+
+```bash
+# Fast responses run with defaults
+pytest -s -v tests/integration --stack-config=server:starter --suite=responses
+
+# Fast single-file vision run with defaults
+pytest -s -v tests/integration --stack-config=server:starter --suite=vision
+
+# Combine suites and override a default
+pytest -s -v tests/integration --stack-config=server:starter --suite=responses,vision --embedding-model=text-embedding-3-small
+```
+
 ## Examples
 
 ### Testing against a Server