Add Message/EngineMessage.effectiveMedia (= message.media when non-empty, else
richText.instantPage.allMedia()) and route the media-consuming sites through it
so a rich message's instant-page media participates in the same pipelines as
normal message.media: shared-media grids/file-rows, search media grid, gallery
open + item nodes + footer, the peer audio/voice playlist, secret-media preview,
resource-by-id resolution, recent downloads, downloaded-media store, delete-time
resource cleanup, cache-usage stats, the in-chat download manager, and the
context-menu / share actions (Save to Camera Roll, copy image, save audio/music
to files). For normal messages effectiveMedia == message.media, so each swap is
behavior-preserving; rich messages render their own bubble via
ChatMessageRichDataBubbleContentNode (not the text/file bubbles), so those paths
are deliberately untouched, as are the forward path (the attribute travels with
the forward) and the markdown-based rich-edit path. First-media scope for now.
See docs/instantpage-richtext.md for the full architecture + invariants.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
