Add vLLM v2.27.0 worker source for Holo4 Hub

[danstotts-ops]

Context

DR-1532 supplied the three Holo4 Hub bundle files, but the new repository had no worker implementation. The Runpod Hub publishing guide requires a Dockerfile and handler.py. Related launch-builder gate work: MOP-729.

Change

• Copy the worker implementation and tests from runpod-workers/worker-vllm tag v2.27.0 at 76054c22c79c515f07065f523598d8efb2f9b682, the version used by the Holo4 template image.
• Add the upstream MIT license and a root handler.py copy for the Hub file requirement. UPSTREAM.md records provenance and the duplicate-file constraint.
• Preserve .runpod/hub.json, .runpod/tests.json, and README.md byte for byte from the newer DR-1532 comment.

Verification

• uv run --no-project --with pytest --with aiohttp --python 3.11 pytest -q tests: 51 passed.
• Both JSON files parse with python3 -m json.tool; Python source compiles; staged diff passes git diff --check.
• Root and src handler.py files compare equal. The three bundle SHA-256 hashes match the prior main commit.
• Docker build remains unverified because Docker Desktop's daemon is unavailable on this host.

Release and listing

The existing launch-20260930 release points to the earlier three-file commit. A new release from main is required after merge so the Hub indexes the worker source. The Runpod Hub Add Repo selector currently shows only danstotts-ops repositories and does not find runpod-workers/worker-holo4, even after the repo became public. No Hub listing was submitted.

[kenlim-mops]

Good provenance record. Copying worker-vllm v2.27.0 at the exact commit used by the Holo4 template image provides Hub audit transparency and the test suite confirms the source is functional (51 passed). UPSTREAM.md records the source tag and the handler.py duplicate constraint. The CI workflow is appropriately minimal: pytest, compileall, cmp handler.py, json.tool on both .runpod files. The note about Docker build being unverified is honest; the Hub builder will handle that. CI green.