stack-encrypt refactor: finalize crate ownership, naming and coordinated migration #1489

The broader packaging proposal is not yet an approved set of crate moves. Track the decision and subsequent migration explicitly.

Acceptance:

• Agree the Stack application-encryption versus Vitamin C primitive/format/encoding boundary and document an acyclic dependency graph.
• Decide the proposed trait/format ownership, AsyncCipher retirement and remaining public naming changes before implementation.
• Reconcile the existing index-crate extraction task stack-encrypt: every index is compiled into the core crate — move Equality, Match, Ore, Ope into their own crates #1063 rather than creating a competing split.
• Keep one canonical trait identity and preserve no-HTTP/WASM builds, feature boundaries and current SQL/engine interoperability.
• Coordinate versioned dependency and consumer updates across Rust, EQL and bindings; preserve released interfaces and stored data/search contracts.
• Update executable examples and migration documentation, then rerun conformance and artifact exchange.

Depends on an explicit architecture decision; this issue does not approve every proposal in #1365. Sequence after customer-facing contract work and the owned API migration (#1488), unless a specific dependency requires an earlier move.

Plan: conformance roadmap and API redesign #1365.