Support dragging notes into chat context

[ComputelessComputer]

Summary

• add a session drag payload for note/session cards
• let chat accept dropped session payloads as manual context
• cover drag payload parsing and chat drop behavior

Verification

• pnpm exec dprint fmt apps/desktop/src/chat/components/content.tsx apps/desktop/src/chat/components/content.test.tsx apps/desktop/src/chat/context/session-drag.ts apps/desktop/src/chat/context/session-drag.test.ts apps/desktop/src/main/top-meeting-timeline.tsx apps/desktop/src/shared/ui/interactive-button.tsx apps/desktop/src/sidebar/timeline/item.tsx
• pnpm -F @hypr/desktop exec vitest run src/chat/context/session-drag.test.ts src/chat/components/content.test.tsx
• pnpm -F desktop typecheck

Fixes #5060

---

Note

Low Risk
UI-only drag/drop and context wiring reusing existing manual refs; malformed payloads are rejected and covered by tests.

Overview
Users can drag note/session cards from the sidebar timeline and top meeting timeline into an active chat so those sessions become manual chat context (same ContextRef path as the context bar).

A new session-drag helper serializes sessionId on a custom MIME type (application/x-anarlog-session-context), with plain-text fallback for the drag preview. ChatContent accepts drops via onDragOver/onDrop and calls onAddContextEntity with a session:manual:* ref; other drag types are ignored.

Timeline session rows and InteractiveButton gain draggable / onDragStart wiring; the top timeline stops pointer propagation on draggable cards so window drag does not fight note drags. Vitest covers payload read/write and chat drop behavior.

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