eqsat — reference

The substrate contract surface, pinned against the phase-1 frozen manifest (graphopt:docs/public_api.md — API_VERSION = "0.1.0").

• The e-graph — the EGraph protocol signature-level: add_term/find/rebuild/run/extract_best, the Rewrite record, and the certificate codec.
• The cost algebra — dag_cost and the shipped cost-model families, signature by signature.
• The ports — Source/Capabilities/Sink/Engine + the rest of the port vocabulary, and signature_conforms.
• The frozen API slice — the substrate rows of the manifest, vendored verbatim.

The conceptual accounts (why these shapes, not just which) live under explanation; the domain-side rows of the manifest are graphopt's and the game rows are gamekit's.