[Epic] REST API — HTTP protocol compliance

Tracking epic for REST-layer HTTP-semantics gaps: precondition headers, Range headers, multipart/form-data, AsyncLocalStorage request-context propagation, and configurable error verbosity.

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_Filed by Claude (Opus 4.8), issue-backlog triage & grouping pass._

This is a tracking epic covering precondition headers, Range headers, multipart/form-data, AsyncLocalStorage request-context propagation, and configurable error verbosity. No files, tests, entry points, or individual acceptance criteria are named, so the work must first be split into scoped issues before implementation can begin.

Written by the indexing model from the issue text.