Function capability_matrix_markdown 

pub fn capability_matrix_markdown() -> String

Render the connector capability matrix as Markdown, derived entirely from the registry allowlists (registry::*_KINDS). Because those are feature-independent const arrays, this output is deterministic regardless of which connectors are compiled in — so a committed copy can be round-trip-asserted in CI (see cli/tests/capability_matrix.rs), which is what stops the matrix from being hand-maintained and drifting (#465 Part 3).

The single source of truth is the allowlists; faucet conformance --matrix prints exactly this, and the parity test (registry_capability_parity) separately proves the allowlists match the trait methods — so the rendered matrix is grounded in real behaviour, not a hand-kept table.