ci: stop sccache flooding the Actions cache quota

[pratyush618]

Problem

The Actions cache quota (10 GB) repeatedly hit its limit — 1,750+ caches, almost all sccache/<hash> entries scoped to a single PR ref.

Root cause: ci-python.yml set SCCACHE_GHA_ENABLED: true, so sccache used the Actions cache API as its backend and wrote one cache entry per compiled rustc object. A full --release maturin build across the matrix minted thousands of tiny entries per push. PR-ref caches can't be read by other PRs, so it was pure churn that evicted the caches that matter.

Fix

• Drop sccache. Cache the release target/ via the existing Swatinem/rust-cache under a dedicated release shared-key — one consolidated entry per OS, master-only writer, PRs restore read-only. Added a shared-key input to the setup-rust composite to keep it separate from the lint job's dev cache.
• Make the Rust lint job a master-only cache writer too (was saving one dev cache per PR ref = unreadable by other PRs = wasted quota).

Net: ~1 release cache/OS + 1 lint cache on master, vs thousands per PR. Entry count drops ~100×.

Existing 1,416 caches already cleared.

Summary by CodeRabbit

• Chores
  • Improved CI build caching for Rust projects to speed up repeated builds.
  • Shared cache keys can now be configured for Rust setup workflows.
  • Limited cache updates to the master branch while allowing pull requests to restore existing caches.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 8e536284-c80a-46bc-a562-3616262c899d

📥 Commits

Reviewing files that changed from the base of the PR and between 807db05 and eaba035.

📒 Files selected for processing (3)

• .github/actions/setup-rust/action.yml
• .github/workflows/ci-python.yml
• .github/workflows/ci-rust.yml

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📝 Walkthrough

Walkthrough

Rust CI caching now supports an optional shared namespace, replaces Python-job sccache usage with release artifact caching, and restricts shared cache writes to the master branch.

Changes

Rust cache behavior

Layer / File(s)	Summary
Shared cache input wiring .github/actions/setup-rust/action.yml	Adds the optional shared-key input and forwards it to Swatinem/rust-cache@v2.
Workflow cache policies .github/workflows/ci-python.yml, .github/workflows/ci-rust.yml	Caches Rust release artifacts under the release namespace and limits cache writes to refs/heads/master; removes the Python job’s prior sccache setup.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• ByteVeda/taskito#310: Updates workflow path filters related to changes in the setup-rust composite action.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main CI caching change: replacing sccache cache usage to prevent GitHub Actions cache quota exhaustion.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/ci-cache-thrash

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