fix: run all clients on stainless SDK, fix workflow, properly commit recordings (#4410)

# What does this PR do?

Various fixes to integration test recording + stainless calling of
integration tests:

1. only the library client was being run, they all should be
2. the git check grabs diffs like:

M tests/integration/client-typescript/package-lock.json
 M tests/integration/client-typescript/package.json

it should not

additionally:

Fixes rebase conflicts when stainless workflow runs integration tests
with
  record-if-missing mode on PRs. Previously, the workflow would:
  1. Commit all files in tests/integration/ (including non-recordings)
  2. Try to rebase and push to 'main' instead of the PR branch
  3. Fail with merge conflicts on PR-specific changes

  Changes:
- Add pr_head_ref and is_fork_pr parameters flowing through workflow
chain
- Use target-branch input instead of github.ref_name in recording
commits
- Detect and handle fork PRs by skipping push and uploading recordings
as artifacts
  - Add 7-day artifact retention for fork PR recordings
  - Support both workflow_call and direct pull_request trigger contexts

For same-repo PRs: recordings now commit/push to the PR branch correctly
For fork PRs: recordings upload as downloadable artifacts with
instructions


you can see a failing workflow:
5846590613
with the rebase issues.

---------

Signed-off-by: Charlie Doern <cdoern@redhat.com>

tests/integration/ci_matrix.json

@@ -7,7 +7,7 @@
     {"suite": "base-vllm-subset", "setup": "vllm"}
   ],
   "stainless": [
-    {"suite": "base", "setup": "ollama", "allowed_clients": ["library"], "inference_mode": "record-if-missing"}
+    {"suite": "base", "setup": "ollama", "inference_mode": "record-if-missing"}
   ],
   "schedules": {
     "1 0 * * 0": [