Terminators and token-frugality knobs (#155 §1/§4):

• .signatures(), .objects(), .paths(), .count()
• .explain() — the plan + backend resolutions + unresolved-edge set; the citation artifact.
• Projection & budget: .select(fields), .limit(n), cursor-based continuation.

The projection/budget knobs are the token-efficiency contract for agent consumers: codeact one-liners return scoped data, never accidental whole-model dumps.

Part of #155. Branch: feat/issue-<n>.