feat(tests): migrate to global "setups" system for test configuration (#3390)

This PR refactors the integration test system to use global "setups"
which provides better separation of concerns:

**suites = what to test, setups = how to configure.**

NOTE: if you naming suggestions, please provide feedback

Changes:
- New `tests/integration/setups.py` with global, reusable configurations
(ollama, vllm, gpt, claude)
- Modified `scripts/integration-tests.sh` options to match with the
underlying pytest options
    - Updated documentation to reflect the new global setup system

The main benefit is that setups can be reused across multiple suites
(e.g., use "gpt" with any suite) even though sometimes they could
specifically tailored for a suite (vision <> ollama-vision). It is now
easier to add new configurations without modifying existing suites.

Usage examples:
    - `pytest tests/integration --suite=responses --setup=gpt`
- `pytest tests/integration --suite=vision` # auto-selects
"ollama-vision" setup
    - `pytest tests/integration --suite=base --setup=vllm`

.github/workflows/integration-tests.yml

@@ -28,8 +28,8 @@ on:
         description: 'Test against both the latest and published versions'
         type: boolean
         default: false
-      test-provider:
-        description: 'Test against a specific provider'
+      test-setup:
+        description: 'Test against a specific setup'
         type: string
         default: 'ollama'
 
@@ -42,18 +42,18 @@ jobs:
 
   run-replay-mode-tests:
     runs-on: ubuntu-latest
-    name: ${{ format('Integration Tests ({0}, {1}, {2}, client={3}, {4})', matrix.client-type, matrix.provider, matrix.python-version, matrix.client-version, matrix.test-suite) }}
+    name: ${{ format('Integration Tests ({0}, {1}, {2}, client={3}, {4})', matrix.client-type, matrix.setup, matrix.python-version, matrix.client-version, matrix.suite) }}
 
     strategy:
       fail-fast: false
       matrix:
         client-type: [library, server]
-        # Use vllm on weekly schedule, otherwise use test-provider input (defaults to ollama)
-        provider: ${{ (github.event.schedule == '1 0 * * 0') && fromJSON('["vllm"]') || fromJSON(format('["{0}"]', github.event.inputs.test-provider || 'ollama')) }}
+        # Use vllm on weekly schedule, otherwise use test-setup input (defaults to ollama)
+        setup: ${{ (github.event.schedule == '1 0 * * 0') && fromJSON('["vllm"]') || fromJSON(format('["{0}"]', github.event.inputs.test-setup || 'ollama')) }}
         # Use Python 3.13 only on nightly schedule (daily latest client test), otherwise use 3.12
         python-version: ${{ github.event.schedule == '0 0 * * *' && fromJSON('["3.12", "3.13"]') || fromJSON('["3.12"]') }}
         client-version: ${{ (github.event.schedule == '0 0 * * *' || github.event.inputs.test-all-client-versions == 'true') && fromJSON('["published", "latest"]') || fromJSON('["latest"]') }}
-        test-suite: [base, vision]
+        suite: [base, vision]
 
     steps:
       - name: Checkout repository
@@ -64,14 +64,14 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
           client-version: ${{ matrix.client-version }}
-          provider: ${{ matrix.provider }}
-          test-suite: ${{ matrix.test-suite }}
+          setup: ${{ matrix.setup }}
+          suite: ${{ matrix.suite }}
           inference-mode: 'replay'
 
       - name: Run tests
         uses: ./.github/actions/run-and-record-tests
         with:
           stack-config: ${{ matrix.client-type == 'library' && 'ci-tests' || 'server:ci-tests' }}
-          provider: ${{ matrix.provider }}
+          setup: ${{ matrix.setup }}
           inference-mode: 'replay'
-          test-suite: ${{ matrix.test-suite }}
+          suite: ${{ matrix.suite }}