feature - package-derived vocab helper bindings from public exports

[dannymeijer]

Summary

v0.6 implements the complete package-derived vocabulary-helper contract: a vocab companion emits checked package helper calls through the same public export surface that ordinary consumers use, with no duplicated Rust-side helper list.

Scope

• Package-public helper discovery and validated namespaced helper-call artifacts.
• Helper eligibility categories, aliases, facade reexports, source spellings, keyword-safe names, and deterministic duplicate/unknown/ineligible diagnostics.
• Package-build validation, checked API metadata, package-consumer equivalence, backend-neutral lowering, documentation, and a real InQL migration.
• Full fixture coverage for ordinary helpers, aliases, reexports, non-helper exports, keyword spellings, stale output, and failure modes.

Boundaries

• No vocabulary-specific package registry, lexical bare-name authority, or generated-Rust helper list.
• Participating packages may migrate incrementally, but the supported contract is complete.

Delivery

• feature - package-derived vocab helper resolution and source-spelling metadata #1031 — package-derived helper resolution and source-spelling metadata
• chore - package-derived vocab contracts, InQL migration, and full conformance #1032 — full contract, InQL migration, and conformance

Done when

• Participating vocab companions require no duplicated helper binding list.
• Package metadata, diagnostics, and consumer behavior agree for every supported helper boundary.
• InQL proves the contract in a non-synthetic package.