feat(fetchers): add GitHub Actions run fetcher

[chaliy]

What changed

Fetch public GitHub Actions workflow run URLs as structured Markdown using GitHub's REST API. Responses summarize run metadata, status, trigger, branch/SHA, timing, jobs, and failed or incomplete steps.

Why

Actions run pages are JavaScript-heavy, and generic HTML fetching provides little useful diagnostic context. The API exposes stable structured run and job data without requiring large log archive downloads.

Before / After

Before: Actions run URLs used generic HTML conversion and omitted useful run diagnostics.

After: Canonical run URLs return format: github_actions_run with workflow/run metadata and up to 100 jobs. Successful steps are omitted while failed or incomplete steps are highlighted.

Proof:

cargo test --workspace: passed
cargo clippy --workspace --all-targets -- -D warnings: passed
RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps: passed
cargo build --workspace --exclude fetchkit-python --release: passed

Risk

• Medium
• Unauthenticated public API requests remain subject to GitHub rate limits.
• Private repository runs return a not-found/private error.
• Job output is limited to the first 100 jobs; the response reports when more exist.

Checklist

• Unit tests are passed
• Smoke tests are passed
• Documentation is updated
• Specs are up to date and not in conflict

Produced by yolop