Document connection-scoped query configuration

[fsistemas]

Summary

Documents the canonical connection_queries schema and syncs the agent skill.

• Adds README coverage for shared/global queries vs connection-scoped queries.
• Documents scoped query resolution precedence and the new --list-queries discovery shape.
• Updates the Docker demo config with a dialect-specific database_name query.
• Updates Python API examples for scoped discovery and effective connection query names.
• Updates repository agent instructions and the canonical sql2json skill.
• Runs the skill sync script to update configured agent skill targets.

Verification

• bash scripts/sync-sql2json-skill.sh — completed
• python -m json.tool docker/config.json >/dev/null — passed
• .venv/bin/python examples/python_api/list_config.py — printed connections, legacy global queries, scoped discovery, and effective default queries
• .venv/bin/python -m pytest -q — 138 passed, 12 deselected
• .venv/bin/black --check sql2json tests examples — passed
• .venv/bin/flake8 sql2json tests examples — passed
• .venv/bin/python -m mypy sql2json — passed