feat: add Artic source role metadata

[baskduf]

Summary

• Add source-role boundary metadata to all 86 Artic catalog entries: source_role, default_visual_reference, and requires_explicit_context.
• Keep runtime source selection behavior unchanged; this PR establishes schema/validation groundwork for later eligibility enforcement.
• Add canonical and plugin self-tests for source metadata, plus catalog search metadata preservation checks.
• Sync Claude/Codex plugin mirrors.

Scope

• PR A only: catalog metadata + validation tests.
• No changes to search scoring, role-grounded selection, init/start lifecycle, or generated runtime output schema.

Test Plan

• python3 -m pytest -q → 101 passed
• python3 skills/artic/scripts/test_artic_scripts.py
• python3 plugins/claude-artic/skills/artic/scripts/test_artic_scripts.py
• python3 plugins/codex-artic/skills/artic/scripts/test_artic_scripts.py
• python3 -m compileall -q skills/artic/scripts plugins/claude-artic/skills/artic/scripts plugins/codex-artic/skills/artic/scripts
• python3 -m build --sdist --wheel
• python3 scripts/build_skill_archive.py --output dist/artic-skill-v0.5.0.tar.gz
• python3 scripts/check_release_artifacts.py --require-payload dist/artic-0.5.0.tar.gz dist/artic-skill-v0.5.0.tar.gz
• python3 scripts/check_release_artifacts.py dist/artic-0.5.0-py3-none-any.whl
• git diff --check
• Independent reviewer pass: no blockers