fix(ci): Making cache write optional, disabling it for the weekly run

[Filter94]

This PR implements issue(s) #

Checklist

• I wrote new tests for my new core changes.
• I have successfully ran tests, style checker and build against my new changes locally.
• If this change is deployed to any environment (including Devnet), E2E test coverage exists or is included in this
  PR.
• I have informed the team of any breaking changes if there are any.

[Copilot]

Pull request overview

This PR adjusts GitHub Actions caching behavior for the arithmetization zkc weekly metrics workflow by making cache usage configurable and disabling (or limiting) cache interactions for the weekly measurement run.

Changes:

• Add cache-enabled input to the arithmetization RISC-V setup action and disable it in the weekly metrics workflow.
• Add cache-enabled input to the zkc measurement setup action and wire it into actions/setup-go caching.
• Add a cache-lookup-only mode to the Zig setup action and pass it through to actions/cache via lookup-only.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/arithmetization-weekly-zkc-metrics.yml	Disables caching for the weekly metrics workflow’s environment setup.
.github/actions/setup-zkc-measurement/action.yml	Introduces a toggle to enable/disable Go caching during zkc measurement setup.
.github/actions/setup-zig/action.yml	Adds restore-only (“lookup-only”) cache mode for Zig cache restores without saves.
.github/actions/setup-arithmetization-riscv/action.yml	Adds cache toggle for Go and ties Zig cache to restore-only when caching is disabled.

Suppressed comments (1)

.github/actions/setup-zkc-measurement/action.yml:40

• The comment here says the Zig cache is restore-only and that dispatched runs "read caches but never save", but this composite action doesn't interact with Zig caching and its Go cache behavior is controlled by inputs.cache-enabled. As written, the comment is misleading; please update it to match the actual caching behavior and the cache-enabled knob.

    # ref alone. Do not add a measured checkout to that job. The measured jobs' Go module/build cache
    # is disabled and the Zig cache runs restore-only (lookup-only), so a dispatched run reads caches
    # but never saves into the refs/heads/main-scoped cache namespace.

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