ci: skip CUDA wheels in mypy/pyright typecheck jobs

[TATP-233]

Summary

• The pyright and mypy jobs ran a bare uv sync, installing torch 2.8.0+cu128 (1.7GB), 72 nvidia-* CUDA wheels (4.1GB), and triton (541MB) — ~6.3GB of the 7.5GB venv — on 1-vCPU ubuntu-slim runners to type-check 106 source files.
• Measured on run 35070480055: pyright job install step 4m55s for a 1m24s check (the analysis itself is ~4s). The benchmark-smoke/test jobs, which already skip the CUDA packages, install in under a minute.
• This PR applies the same pattern to both typecheck jobs: skip torch/nvidia-*-cu12/triton during uv sync, install CPU torch==2.8.0 (matches the version pinned in uv.lock; torch's .pyi stubs are identical between CPU and CUDA builds), and switch the Check steps to uv run --no-sync so uv does not re-sync the swapped torch back to the cu128 build.
• No user-facing or training-impact behavior; CI only.

Linked Work

• Issue: ci: typecheck jobs (pyright/mypy) install 6.3GB CUDA wheels they never use #1597
• Parent roadmap (when applicable): n/a
• Roadmap declared base (when applicable): n/a
• Milestone: n/a
• Base branch: main

Validation

• make test-all passed on the final local head before this PR was created or updated
• Additional task-specific validation listed below

Commands actually run:

make test-all
# ruff format/check: OK; mypy: Success, 128 files; pyright: 0 errors, 1 warning
# pytest: 1474 passed, 26 skipped, 588 deselected; benchmark smoke: 34/34 + 35/35

# Faithful CI-env replication in a scratch venv (uv sync with the new
# --no-install-package list + CPU torch 2.8.0, no nvidia/triton):
uv run --no-sync pyright --venvpath /tmp/pyrightcheck   # 0 errors, 7 warnings
UV_PROJECT_ENVIRONMENT=/tmp/pyrightcheck/.venv uv run --no-sync mypy src/unilab  # Success, 128 files

The 7 pyright warnings are all reportMissingImports for optional extras (mujoco, glfw, drake_uni) that are equally absent from today's CI pyright env (bare uv sync installs no extras) — check results are unchanged.

Remote CI route:

• Base main: current-head CI run https://github.com/Motphys/UniLab/actions/runs/35073718861 — all jobs success. Measured on this head: pyright install 47s + check 26s (was 4m55s + 1m24s); mypy install 29s + check 10s (was 3m05s + 23s).

Impact

• Backend impact: none
• Platform impact: Linux CI runners only
• Training effect expected: no

Artifacts

• W&B: n/a
• benchmark result: n/a
• video / screenshot: n/a
• ONNX / checkpoint: n/a

Checklist

• Added or updated tests where needed (n/a — workflow-only change)
• Updated docs if behavior or workflow changed (n/a — no policy/workflow-doc change; the ci.yml pattern is copied from existing jobs)
• Linked the driving issue
• Noted any follow-up work explicitly (the test job still installs CPU torch 2.7.0 while uv.lock pins 2.8.0; aligning it is a separate concern)