Python gate parity: ruff, ruff format, pyright, pytest in one command and in CI #4865

Part of the agentic software factory tracker #4858, Wave 2. Proposed as S4 in docs/agent-guidance-inception.md (PR #4861) §9, from #4859.

Depends on

None beyond #4859. Can run in parallel with the rest of Wave 2.

Scope

• For each of fetch, git and time, one per-server validate entry runs ruff check, ruff format --check, pyright, pytest and uv build. CI already gates the build. It can be a uv run chain or a scripts/ helper.
• A root command (e.g. npm run validate:py) runs all three servers.
• python.yml runs ruff: ruff is a dev dependency of every server but isn't run in CI today.
• Add the Python rules to AGENTS.md. If Part 2 (AGENTS.md, AGENTS.md: the absolute rules; delete CLAUDE.md #4862) hasn't merged yet, hand them to it instead.

Acceptance criteria

• One root command gates every Python server.
• CI fails on a ruff lint or format finding.
• Existing findings are fixed, not suppressed through config.

Branch

Targets v2/main. Closes #N won't auto-close an issue on a non-default branch, so close this one by hand on merge and move the card to Done.