Report new rustqual findings from cargo_check

• Status: Todo
• Kind: Feature
• Authors: jp
• Date: 2026-10-06
• Label: domain=tooling
• Label: type=task

Make the cargo_check tool (.config/jp/tools/src/cargo/check.rs) report the rustqual findings that CI would fail on, so an assistant can find out before pushing. It uses the qual crate from T-0yh5frr as a library, so it gives the same verdict and the same messages as CI.

Behaviour

• Add a QualCheck step next to ComfortCheck, with the same Clean / Findings(note) / Failed(stderr) shape.
• Run it only after clippy succeeds: findings on code that doesn't compile are noise.
• The head is the working tree, including uncommitted changes. The base is merge-base(HEAD, origin/main), falling back to main when there's no remote, and its report is cached by qual.
• The package parameter filters which findings are reported, not what is analysed. Dead-code and duplicate detection need the whole workspace.
• Render in the AI-oriented format with per-rule guidance, and list the allowed escape hatches (see the escape-hatch ticket).
• Update the tool summary in .jp/mcp/tools/cargo/check.toml, and the rust-development skill description if it lists what cargo_check covers.

Tests

Follow check_tests.rs: cover clean, findings and failure with MockProcessRunner, plus the case where clippy fails and the qual step is skipped.