Why: the delivery log for the 2026-09-30 afternoon fixes (part-order
fidelity, download channel, artifact file management, settings cascade)
belongs with the redesign proposal it extends, including the two durable
conventions it produced.
Evidence: adds section 9 with root causes, the render-order-equals-
storage-order rule, the compound-selector lesson for @ui shells on host
generic classes, and the full verification record (vitest/go suites plus
the 12/12 headless run).
Impact: future UI work inherits both conventions without rediscovering
the failure modes.
Refs: task feature/chat-order-artifact-files.
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