feat(worker): publish py3.13 image variants

[deanq]

Summary

Adds Python 3.13 to the worker image CI matrix. No Dockerfile changes required — the base image runpod/pytorch:1.0.3-cu1281-torch291-ubuntu2204 already ships python3.13 at /usr/bin/python3.13 (verified via docker run ... python3.13 --version → Python 3.13.11). The existing non-3.12 install path (pip bootstrap + torch reinstall + symlink repoint) handles 3.13 unchanged.

What's in this PR

.github/workflows/ci.yml: 3.13 added to the four docker-test-* matrices (build/test) and to the four docker-prod-* include-style matrices (release-build). One commit, +12/-4.

Why this is small

An earlier revision added a deadsnakes-PPA install for 3.13 — that was unnecessary (the base already has it) and introduced a supply-chain concern flagged by Copilot. Dropped via force-push. Verifying that python3.13 --version works directly from the base is enough.

Verification

• docker run --rm runpod/pytorch:1.0.3-cu1281-torch291-ubuntu2204 python3.13 --version → Python 3.13.11
• Local docker buildx build --build-arg PYTHON_VERSION=3.13 -f Dockerfile . advances past python3.13 --version into the torch-install step (local QEMU runs hit transient network read errors on the 700 MB torch wheel; CI on native amd64 will handle it).
• Torch 2.9.1+cu128 cp313 wheel confirmed available at https://download.pytorch.org/whl/cu128/torch/

Linear

AE-3152 (child of AE-2827)

Test plan

• CI matrix green for py3.13 × {gpu, cpu, lb, lb-cpu}
• After release-please merge, runpod/flash:py3.13-{gpu,cpu,lb,lb-cpu} exist on Docker Hub
• Pulled py3.13-gpu image startup version assertion prints Python 3.13 OK

[Copilot]

Pull request overview

Adds Python 3.13 as an additional published worker-image variant by installing python3.13 via deadsnakes on the GPU-based images (which don’t ship 3.13) and expanding the CI build/release matrices accordingly.

Changes:

• Add conditional deadsnakes-based install of python3.13 (plus -venv/-dev) in Dockerfile and Dockerfile-lb when PYTHON_VERSION=3.13.
• Expand GitHub Actions docker test matrices to include Python 3.13 across cpu/gpu/lb variants.
• Expand GitHub Actions docker production include matrices to publish 3.13 tags (non-default).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
Dockerfile	Installs Python 3.13 from deadsnakes PPA for GPU image when requested.
Dockerfile-lb	Mirrors GPU Dockerfile change for the load-balancer image variant.
.github/workflows/ci.yml	Adds 3.13 to docker test and prod publish matrices.

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