Define local-first universal chat foundation

[Peyton-Spencer]

What changed

• rewrites the V2 plan around the actual product goal: agent tasks and human chats in one desktop app
• makes local/no-account operation the default and Ditto sign-in an optional cloud-continuity upgrade
• defines hosted and device transports as separate capabilities for each service
• adds normalized channel/account/conversation/message/capability contracts shared by desktop, server, web, and future hosted workers

Important boundary

Discrawl is the fast local Discord archive/index. Its device-cache mode is read-only, partial, and never extracts a user token or runs a selfbot. Discord bot transport is modeled separately for official bot-identity sending.

Why

The UI must render from a live capability snapshot instead of promising fake platform parity. This contract supports device and hosted transports side by side while keeping DMs local-only unless the user explicitly enables cloud mirroring.

Validation

• vp check (passes; repository has pre-existing warnings)
• vp run typecheck

Stack

Depends on #1. The Discord/iMessage adapter layer is #3.

Note

Add channels.ts contracts module and Ditto Desktop V2 plan doc

• Introduces channels.ts defining runtime-decodable effect/Schema schemas and types for chat channels: capabilities, conversations, messages, send inputs/results, and ChannelOperationError.
• Re-exports the new module from the contracts barrel in index.ts so all channel symbols are available via the top-level import path.
• Adds ditto-desktop-v2-plan.md outlining workstreams, sequencing, decisions, and the release pipeline for Ditto Desktop V2.

^{Macroscope summarized 9965f94.}

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	13.3 KiB	—	15.1 KiB	✅
Codex	Thread snapshot wire	—	6.9 KiB	—	7.3 KiB	✅
Codex	Live turn WebSocket wire	—	6.4 KiB	—	7.8 KiB	✅
Codex	Live turn WebSocket decoded	—	55.6 KiB	—	66.4 KiB	✅
Codex	Live turn messages	—	11	—	21	✅
Claude	Total thread wire	—	13.4 KiB	—	15.1 KiB	✅
Claude	Thread snapshot wire	—	6.9 KiB	—	7.3 KiB	✅
Claude	Live turn WebSocket wire	—	6.5 KiB	—	7.8 KiB	✅
Claude	Live turn WebSocket decoded	—	56.4 KiB	—	66.4 KiB	✅
Claude	Live turn messages	—	11	—	21	✅

Baseline: unavailable · PR result: 9965f94 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 109.4 KiB
• Claude decoded thread snapshot: 110.1 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.