plugin: describe Speak Swiftly marketplace entry

[gaelic-ghost]

Summary

• add display metadata and a clearer description for the Speak Swiftly Socket marketplace entry
• remove stale lint-only failures in child skill maintainer scripts
• bump shared maintained version surfaces to v6.6.7

Subtree Accounting

• apple-dev-skills touched by the shared version bump and lint cleanup; subtree push/release accounting is required before final Socket release closeout
• no subtree pull was required before this PR because the changes were authored in Socket

Verification

• uv run scripts/validate_socket_metadata.py
• uv run pytest
• uv run ruff check .
• cd plugins/apple-dev-skills && bash .github/scripts/validate_repo_docs.sh
• cd plugins/apple-dev-skills && uv run pytest

Blocked Check

• uv run mypy . is blocked by duplicate top-level customization_config.py modules across skill script directories; no patch files introduced that module layout