feat(research): add shared history presentation model

[hubab1]

Summary

• add an @MainActor observable presentation model for paged research history
• preserve shared query-result evidence without inferring an App Store rank for a pre-live project
• reject stale membership generations, merge pages deterministically, and reconcile committed refreshes before continuing offset pagination
• restore truthful load state across cancellation races and cover paging, reincarnation, ordering, and stale-publication behavior

Stack

• base: feat(research): add project detail presentation model #53
• roadmap slice: 34d, shared research-history presentation state

Validation

• 5 focused KeywordResearchHistoryModelTests passed
• 442 tests pass at this stack boundary; 445 passed at the current stacked UI head
• signed Debug build passed
• strict deep code-signature verification passed
• independent P1/P2 review clear
• GitHub Actions is green for the rebased head
• no live-store launch was performed because this stack includes the V5 schema work

Authorship

Implemented independently for this repository; no co-author trailer applies.