Save warp cache for CI

[StafaH]

Description

Save warp cache post-merge so future CI can run warm.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Summary

This PR wires up a Warp kernel cache across the CI pipeline so that the expensive per-job kernel compilation happens once post-merge and is reused by subsequent PR runs. It introduces two new composite-action inputs (warp-cache-family and warp-cache-write), an nvidia-smi–driven GPU identity step, GitHub Actions cache restore/save bookends, and a Python fail-fast check that confirms the container actually honours WARP_CACHE_PATH before tests start.

• run-package-tests: resolves GPU compute capability with sort -u | paste -sd- (multi-GPU safe), restores the Warp cache before the test container starts, saves it on success() only when warp-cache-write == 'true' and there was no exact cache hit.
• run-tests: accepts warp-cache-host-dir as the 22nd positional argument, bind-mounts it into the container as /tmp/isaaclab-warp-cache:rw, sets WARP_CACHE_PATH, and validates the path via wp.config.kernel_cache_dir — surfacing any env-var naming mismatch as an immediate job failure.
• build.yaml: removes the github.event_name != 'push' guard from the tasks, core, and newton jobs (enabling post-merge runs), assigns a unique warp-cache-family per shard, and gates warp-cache-write on push or workflow_dispatch events only.

Confidence Score: 5/5

Safe to merge — all three files are CI-infrastructure only, the cache is gated behind success() so broken test runs never pollute the cache, and the Python sanity check turns any WARP_CACHE_PATH misconfiguration into an immediate, visible job failure.

The logic is tight: the GPU identity step covers multi-GPU runners via sort-unique join; the save condition guards on warp-cache-family, warp-cache-write, success(), and cache-hit; and the in-container path validation catches any env-var naming drift at job startup rather than silently writing to the wrong location. The only observable change to production behavior is that the tasks/core/newton jobs now also run on push events — intentional for cache warming.

Files Needing Attention: No files require special attention.

Important Files Changed

Filename	Overview
.github/actions/run-package-tests/action.yml	Adds warp-cache-family/warp-cache-write inputs, GPU-capability identity step (sort -u
.github/actions/run-tests/action.yml	Accepts warp-cache-host-dir as positional arg 22, mounts the dir into the container as /tmp/isaaclab-warp-cache:rw, sets WARP_CACHE_PATH, and adds a Python fail-fast sanity check via wp.config.kernel_cache_dir
.github/workflows/build.yaml	Removes github.event_name != 'push' guards from tasks/core/newton jobs, assigns per-shard warp-cache-family names, and enables warp-cache-write on push and workflow_dispatch events only

Sequence Diagram

sequenceDiagram
    participant WF as build.yaml
    participant PKG as run-package-tests
    participant GHC as actions/cache
    participant RT as run-tests
    participant CTR as Docker Container

    WF->>PKG: "warp-cache-family=isaaclab-tasks-0<br/>warp-cache-write=true (on push)"
    PKG->>PKG: "Resolve Warp cache identity<br/>(nvidia-smi → sort -u | paste -sd-)"
    PKG->>GHC: "cache/restore@v4<br/>key: warp-v1-{family}-{os}-{arch}-{gpu}-{isaacsim}-{hash}-{epoch}"
    GHC-->>PKG: "restored (cache-hit=true/false)"
    PKG->>PKG: "mkdir -p cache_dir && test -w"
    PKG->>RT: "warp-cache-host-dir=/tmp/runner/isaaclab-warp-cache/isaaclab-tasks-0"
    RT->>CTR: "docker run -v host_cache_dir:/tmp/isaaclab-warp-cache:rw<br/>-e WARP_CACHE_PATH=/tmp/isaaclab-warp-cache"
    CTR->>CTR: "wp.init() + verify wp.config.kernel_cache_dir == WARP_CACHE_PATH"
    CTR->>CTR: run pytest (compiles Warp kernels into /tmp/isaaclab-warp-cache)
    CTR-->>RT: exit code
    RT-->>PKG: result
    PKG->>PKG: Check Test Results (if always())
    alt "success() && warp-cache-write=='true' && cache-hit!='true'"
        PKG->>GHC: "cache/save@v4 (key = cache-primary-key)"
    end

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_{Reviews (2): Last reviewed commit: "Merge branch 'develop' into mh/ci-warp-c..." | Re-trigger Greptile}

[StafaH]

@greptileai