Make Markdown Queryable

Query imperfect Markdown in one of two modes:

• Read-only query: Query a document with or without an mdq profile. Use existing metadata when valid; otherwise let the CLI infer temporary in-memory selectors and return source-located evidence.
• Persistent query contract: On an explicit user request, add or repair a small declarative YAML mdq profile and optionally stable markers or a sidecar index.

The profile is a reusable optimization and contract for deterministic, source-located queries. It is not a prerequisite for answering a one-off question.

Core Rules