build: bump actions/cache to v6

[lachieh]

build: bump actions/cache to v6

GitHub deprecated the Node 20 runtime on runners. They now force anything still pinned to Node 20 to run on Node 24 anyway, so this isn't a functional break — the cache already runs on 24. The only thing we get is a deprecation warning on every run:

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v4.

setup-nub wraps actions/cache in its "Cache nub store" step, so every consumer inherits that warning (e.g. "Detect server changes / Node.js 20 is deprecated" in the murals.plus pipelines). This just bumps the embedded step from actions/cache@v4 to actions/cache@v6 to silence it. Key, paths, and restore-keys are unchanged.

[pullfrog]

no API key found — Pullfrog needs at least one LLM provider API key (e.g. ANTHROPIC_API_KEY, OPENAI_API_KEY, GEMINI_API_KEY) configured as a GitHub Actions secret.

To fix: add the key as a GitHub Actions secret (referenced from your workflow's env: block) or as a Pullfrog secret in the console — or switch this repo to a different model (free models need no key).

Open repo secrets → · Configure model → · Setup docs → · Ask in Discord →

  ^{｜ Rerun failed job ➔ ｜ View workflow run ｜ via Pullfrog ｜ 𝕏}

[GuptaSiddhant]

@colinhacks could this be merged to enable better dev-exp.