[ITSGJY]

Summary

• Add Python Ruff lint (check) and formatting validation (format_check) to the existing project_validate gateway, alongside the established Python pytest, Rust, and Go paths.
• Bind the Runner-owned command to a bounded project-local pyproject.toml Ruff configuration with an explicit target version and stable manifest provenance. Revalidate the plan at Job admission and after queueing.
• Execute Ruff through one selected Python environment using matching isolated module probes and canonical python -I -B -m ruff steps. Lint and format validation keep file modifications disabled.
• Add a dedicated Runner capability, separate Ruff check/format validation identities, evidence profiles, and Workflow Session retention without expanding the model-facing tool surface.

Verification

• Offline focused Rust suites after rebasing onto the latest fork main: 8 Core, 118 Validation, 28 Runner, 9 Runner Registry, and 266 Workflow Session tests passed. Five pre-existing ignored Workflow Session tests remain ignored.
• cargo fmt --all -- --check and git diff --check: passed.
• Ruff 0.16.9 was executed from a temporary, hash-verified official PyPI wheel on Linux aarch64. Both canonical commands reported known lint/format discrepancies, preserved source under fix=true and fix-only=true, and left no Ruff or bytecode cache. A project-local ruff.py was not executed. The temporary environment was removed.
• Focused Codex and agy read-only source reviews: PASS.

This fork PR is the full-CI validation lane before considering an upstream contribution. Part of yyjeqhc#962.

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