[lukaszstolarczuk]

Line coverage from tests and examples in tests.yml.

• Add helper coverage job after tests, it combines the data, compares it
  against the latest main and runs diff-cover on changed lines, on PRs.
• Results are published in the job summary.
• PRs fail if total coverage drops by more than 5%.

[lukaszstolarczuk]

tested on my branch:
https://github.com/intel/torch-tweak/actions/runs/40694536085/job/122844190343#step:11:27

badge preview:
https://github.com/intel/torch-tweak/tree/add-coverage#torch-tweak

[Copilot]

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Copilot review overview

7 open issues

• This workflow isn’t defined as workflow_call/workflow_dispatch here, so the inputs context is… · New
• Units are inconsistent: the summary uses percentage points (pp), but the emitted ::error… · New
• Units are inconsistent: the summary uses percentage points (pp), but the emitted ::error… · New
• PR description says PRs fail if total coverage drops by more than 10 percentage points, but the… · New
• Correct typo in help text: 'then' should be 'than'. · New
• This text is user-facing in the job summary and is Windows-path specific (htmlcov\\index.html).… · New
• Step name says coverity but it updates a coverage badge. Rename to Update coverage badge to… · New

What changed in this PR

Adds CI line coverage reporting, including combining coverage from tests + examples, comparing against a main baseline, and reporting changed-line coverage via diff-cover.

Changes:

• Collect coverage during unit/functional tests and example runs, then upload raw coverage data as an artifact.
• Add a dedicated coverage job to combine reports, compare against main, run diff-cover, and publish a GitHub Actions summary/notice.
• Document coverage measurement locally and add a README coverage badge.

File	Description
pyproject.toml	Adds coverage tooling deps/groups and configures coverage.py (paths, parallel, reporting).
examples/​LLM/​pyproject.toml	Adds a lightweight dependency group to enable coverage measurement in the example venv.
examples/​E5Large/​pyproject.toml	Adds a lightweight dependency group to enable coverage measurement in the example venv.
README.md	Adds a coverage badge pointing to a generated gist badge.
CONTRIBUTING.md	Documents how CI measures coverage and how to run coverage locally.
.github/​workflows/​tests.yml	Runs tests/examples under coverage, uploads artifacts, adds a post-job coverage comparison/summary job, and attempts to update a badge.
.github/​scripts/​coverage_summary.py	New script to compare current vs baseline coverage and render a job summary + notice + failure threshold.

_{Review effort: Lite}