On opening the floating AI-chat window from the header on a document page,
auto-open the LAST chat bound to that document. Binding reuses the existing
ai_chats.page_id (no migration): the bound chat is the requesting user's
most-recent non-deleted chat created on that page, so a new chat on the page
becomes the bound one for free. Resolution happens only on a genuine
closed -> open transition; the provenance badge deep-link is untouched.
Server: AiChatRepo.findLatestByPage + POST /ai-chat/bound-chat (BoundChatDto),
both read-only and owner/workspace-scoped.
Client: getBoundChat service + useOpenAiChatForCurrentPage hook wired into the
app-header entry point (fail-soft to a fresh chat; draft/role cleared only on a
real switch).
Tests: repo scoping/ordering, controller wiring, and hook behavior.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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