docs: audit Typed* contract and propose prefix-free naming

[blackopsrepl]

Motivation

• Audit the current Typed*/typed_* surface to determine whether the explicit Typed prefixes are necessary and to propose a unified, prefix-free naming model plus a migration plan.

Description

• Add docs/typed-contract-audit.md which inventories public Typed* usages, documents the structural role of the descriptor adapter (TypedEntityExtractor), and proposes renames (e.g. TypedValueSelector -> ValueSelector) and an atomic, no-shim migration strategy; this is a documentation-only change.

Testing

• Ran automated repository scans (rg searches for Typed/typed_* patterns) and git status, and committed the new file; all commands completed successfully.

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Codex Task

[blackopsrepl]

Superseded by #31, which keeps the audit rationale and pairs it with the actual release-branch implementation.