feat: establish standalone Argand Site Registry

docs/CONSUMERS.md

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+# Consumer and compatibility contract
+
+## Rust library
+
+Use `argand_site_registry::query::Registry::open(generation, trusted_pin)` once per
+immutable generation and reuse the reader. `lookup(query, limit)` returns evidence
+and complete ambiguity counts; `resolve(query, locale, country, now)` returns an
+optional reviewed candidate. Check the compiled example and API docs for exact
+types. `selection_context` binds the full alternative set for downstream query
+review. Preserve the returned provenance, scopes, counts and attribution.
+
+For local integration, point a Cargo dependency at
+`crates/argand-site-registry` inside an extracted standalone source tree. Once an
+upstream repository is published, use its actual Git URL and a full reviewed `rev`
+pin. Do not invent a crates.io version or track a mutable branch in production.
+Both crates remain in this workspace; the atomic helper is a relative dependency.
+
+## CLI and other languages
+
+`lookup`, `resolve`, `verify` and the other commands emit JSON. The Python example
+passes arguments directly to the native executable, preserving query text and the
+entire response. A nonzero exit is an error. `destination: null` is a successful
+abstention, not a request to pick the first lookup candidate. Render source names
+as untrusted text and satisfy their source-specific attribution requirements.
+
+Use a bounded process or service wrapper appropriate to your workload. The Python
+example has a 60-second timeout and invokes a fresh reader per request; for repeated
+low-latency queries, use the reusable Rust reader. No hosted API or Python package
+registry publication is claimed by this repository.
+
+## SQLite, JSONL and license scope
+
+Distribute `registry.sqlite`, `COMPLETE.json`, `LICENSE_SOURCES.md` and
+`ATTRIBUTION.json` together, plus the publisher signature when applicable. The
+database contains audit records and source descriptions. Default JSONL export
+omits descriptions and includes fact provenance plus an attribution envelope.
+It is an assertion export, not a self-contained signed list of admitted routes.
+Raw SQL inspection is useful for audit; it does not implement resolution policy.
+
+Code version 0.1.0 is an initial interface. Schema/rule contracts are versioned
+independently in receipts. Unsupported contracts fail closed. Pin source releases,
+compile consumers and replay fixed fixtures before upgrades. Preserve import and
+review history; never mutate complete generations to migrate them.
+
+## Argand transition
+
+UPSTREAM.json pins the exact Argand source baseline, including the beta agent's
+selection-context API. The first standalone extraction preserves runtime Rust and
+migration bytes. Argand currently consumes its embedded workspace crate; this
+package does not silently redirect that dependency.
+
+At cutover, coordinate with the Argand source/build owner, compare both trees with
+the recorded baseline, carry any subsequent fixes forward, replace the embedded
+dependency with a reviewed standalone revision, and run Argand's complete engine
+and navigation-compiler gates. Preserve existing registry receipts and public
+navigation admission. After cutover, develop the library upstream and update
+Argand through explicit pinned dependency changes, avoiding permanent dual copies.