Preserve emitted Assembly metadata and future response errors

[kvz]

The SDK currently rejects valid Assembly responses already emitted by API2: numeric State/XPSubject, repeated date tags and null upload extensions. A closed response-error enum also rejects future server errors. Correct those readers and exported response types in a separate breaking PR, as Kevin requested, instead of hiding a type break inside the patch alphalib sync.

Merged after #539, with this PR retargeted to main and current main merged before the final green CI run.

• Preserve finite numeric metadata and mixed repeated date values without coercion; reject booleans, nonfinite numbers and nested arrays.
• Accept nullable completed-upload extensions and nonempty future response errors in status and list APIs. Keep the 371-code known inventory closed.
• Recognize future terminal errors while retaining busy/success states with explicit undefined errors. Preserve known-code autocomplete in hasError while allowing future codes.
• Include majors for node, transloadit, types and zod, and pre-1.0 minors for MCP and the notification relay (which publicly exports the same AssemblyResponse type). The migration guide describes the widened fields and required narrowing. The approved release was published through Version Packages #544: node, transloadit, types and zod 6.0.0; MCP 0.6.0; notification relay 0.3.0. All six npm versions and latest dist-tags, matching Git tags, published GitHub Releases and final main CI are verified.

Validation: the actual SDK HTTP response fixture first failed 13 cases; the focused response/lean suites now pass 123 tests. Review exposed four busy/success classification regressions, demonstrated red and fixed green. TypeScript's language service demonstrated missing known-code suggestions before the correction and now suggests all 371 codes. Full SDK check/verify chains, Zod v3/v4 runtime parity and public declaration equality, clean-output generators, dependency/publish guards and package parity pass. Packed entry points, manifest and file inventory stay identical to the sync parent; changes are confined to Assembly Status source and compiled declarations/runtime/maps. Node 20.10 support remains unchanged.