ci: add diff-aware 80% coverage gate (Vitest + cargo-llvm-cov)

[senamakel]

Summary

• New .github/workflows/coverage.yml enforces ≥80% coverage on changed lines (not whole files) for every PR.
• Three coverage producers in parallel: Vitest for app/, cargo-llvm-cov for the openhuman core crate, and cargo-llvm-cov for the Tauri shell (app/src-tauri).
• Final coverage-gate job runs diff-cover --fail-under=80 against origin/<base_ref> over all collected lcov files, uploads HTML + Markdown reports as artifacts.

Notes

• Vitest already emits lcov (see app/test/vitest.config.ts); a sed step rewrites SF:src/... → SF:app/src/... so paths align with git diff from the repo root.
• RUSTC_WRAPPER=sccache is disabled for the coverage jobs — sccache mis-caches -C instrument-coverage builds. Swatinem/rust-cache still warms target/.
• Test files are excluded from lcov reports already (Vitest coverage.exclude, cargo-llvm-cov #[cfg(test)] filtering), so changed test lines are not measured and don't skew the ratio.
• After merge, add Coverage Gate (diff-cover ≥ 80%) as a required status check in branch protection for main.

Test plan

• First run on this PR succeeds and produces a diff-coverage-report artifact.
• Verify each lcov-* artifact is non-empty (frontend, rust-core, rust-tauri).
• Confirm the gate would fail by opening a follow-up PR that adds an uncovered function and watching Coverage Gate go red.
• Confirm gate path normalization works: changed file paths in the report match repo-root-relative paths.
• Tauri-shell coverage job completes within an acceptable wall time after CEF/Rust caches warm.

Summary by CodeRabbit

• Chores
  • Added automated code coverage verification to the CI/CD pipeline for pull requests, ensuring quality standards are maintained across all components.

[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: 6fefc7ae-7f86-4fcd-95dc-c721b5b481d6

📥 Commits

Reviewing files that changed from the base of the PR and between 3c292b2 and c7d24d2.

📒 Files selected for processing (1)

• .github/workflows/coverage.yml

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📝 Walkthrough

Walkthrough

A new GitHub Actions workflow adds coverage tracking for pull requests, running Vitest coverage for the frontend and cargo llvm-cov for the Rust core and Tauri crates, then using diff-cover to gate PRs on 80% coverage of changed lines.

Changes

Coverage Gate Workflow

Layer / File(s)	Summary
Workflow Triggers & Base Configuration .github/workflows/coverage.yml (lines 1–10)	Workflow triggers on pull requests and manual dispatch with minimal permissions and concurrency cancellation.
Frontend Coverage Job .github/workflows/coverage.yml (lines 11–55)	Checks out code, installs pnpm and Node.js 24.x, runs pnpm test:coverage under app/, normalizes lcov.info paths with app/ prefix, and uploads the report as lcov-frontend artifact.
Rust Core Coverage Job .github/workflows/coverage.yml (lines 56–90)	Runs Rust 1.93.0 container with system dependencies (cmake, ALSA, X11 libs), caches Rust artifacts, executes cargo llvm-cov -p openhuman, and uploads lcov-core.info as lcov-rust-core artifact.
Rust Tauri Coverage Job .github/workflows/coverage.yml (lines 91–132)	Runs Rust 1.93.0 container with extended caching for app/src-tauri and tauri-cef distribution, executes cargo llvm-cov against app/src-tauri/Cargo.toml, and uploads lcov-tauri.info as lcov-rust-tauri artifact.
Coverage Gate & Reporting .github/workflows/coverage.yml (lines 133–190)	Downloads all lcov-* artifacts, installs Python 3.12 and diff-cover, fails if no LCOV files are found, runs diff-cover with --fail-under=80 against the base branch, and uploads HTML/Markdown reports regardless of threshold pass/fail.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 Through workflows we hop, with coverage so tight,
Vitest and Cargo join forces to fight,
Three jobs dance together, their reports take flight,
Then diff-cover gates check—eighty's the height!
A patchwork of tests now shines crystal bright! ✨

🚥 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 PR title clearly and concisely summarizes the main change: adding a diff-aware 80% coverage gate using Vitest and cargo-llvm-cov for CI.
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.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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