feat: add agent skills for PR workflows and cross-repo sync

[shatakshiiii]

Summary

• Add 4 agent skills (pr-new, pr-review, pr-contributor-review, tox) adapted from ansible/apme for team-devtools
• Add centralized sync-skills GitHub Actions workflow to propagate skills to 10 consumer repos
• Update AGENTS.md with skills reference table

Changes

• .agents/skills/tox/SKILL.md — Tox environment reference adapted to team-devtools envs (lint, py, docs, pkg, devel, deps)
• .agents/skills/pr-new/SKILL.md — PR submission workflow with quality gates, conventional commits, and PR template
• .agents/skills/pr-review/SKILL.md — PR review handling: responding to comments, GraphQL thread resolution, Copilot patterns, deferred work tracking
• .agents/skills/pr-contributor-review/SKILL.md — Contributor PR review checklist: upstream sync, quality gates, description quality
• .agents/skills/README.md — Skills index
• .github/workflows/sync-skills.yml — Centralized workflow that syncs skills to 10 repos (weekly + on change + manual dispatch)
• AGENTS.md — Added Agent Skills section with invocation table

Key adaptations from apme

• tox -e unit → tox -e py (team-devtools naming)
• Removed all SDLC/ADR, gRPC, container/pod, rule catalog references
• Updated CI failure patterns for team-devtools hooks (biome, tombi, ansible-lint)
• All repo references point to ansible/team-devtools

Sync workflow details

• Pushes .agents/skills/ to: ansible-compat, ansible-creator, ansible-dev-environment, ansible-dev-tools, ansible-lint, ansible-navigator, molecule, pytest-ansible, tox-ansible, vscode-ansible
• Triggers: weekly Monday 08:07 UTC, on .agents/skills/** changes to main, manual dispatch
• Direct commit to main (markdown-only, non-runtime changes)
• Uses existing BOT_PAT from ack environment

Test plan

• Review all skill files for correctness and no apme-specific references
• Verify sync-skills workflow YAML is valid
• After merge, trigger sync-skills via workflow_dispatch and verify skills appear in a target repo

Related: AAP-71791