chore: update docs, config, and planning artifacts

fix: resolve 6 TypeScript type errors across notes, research, and engine

feat: wire cross-feature integration flows

feat: add consensus report card and Find Consensus pill in chat

feat: add paper search and DOI import to Research Hub

feat: add citation discovery graph to Research Hub

feat: add Research Hub page with sidebar and paper detail

feat: add drag-to-embed and pin-to-note for mini-chat threads

feat: add Research Hub to main navigation

feat: add Writer Mode with 5 format presets and plain text sub-mode

feat: add chat-embed block type for inline note chats

feat: add consensus SSE API route

feat: add writer mode state (editor mode, format, sub-mode) to notes slice

feat: extend research slice with collections, saved papers, consensus reports

feat: implement consensus engine with 5-stage pipeline