feat(magi): add weighted consensus across providers

[Quicksaver]

Summary

Magi lets a conversation ask several model participants to assess a candidate and reach weighted consensus. The conversation's existing agent arbitrates the result, so users can combine providers without handing their task to a separate coordinator.

Users can arm the next message, including a new conversation's first message, or explicitly ask the agent to start Magi during a turn. Consensus never expands the initiating request's permission to act.

What changed

• Add a fixed participant roster, weighted candidate and proposal voting, incompatible-proposal decisions, and an audit history owned by the conversation.
• Persist run state, participant conversations, evidence artifacts, approvals, actions, cancellation, and recovery through the server's existing orchestration and migration ledger.
• Integrate Codex, Claude, Cursor, Grok, OpenCode, and Antigravity through shared provider capabilities, including context limits and supported native compaction.
• Add web settings and a conversation panel for roster configuration, arming, live runs, participant approvals, and history. Mobile opens Magi through the header menu for existing conversations and new-task drafts.
• Keep participant conversations out of the ordinary sidebar and preserve their evidence with the owning conversation's archive and deletion lifecycle.

Validation

216 focused tests passed across 25 files; branch diff check passed.

• vp test run apps/server/src/magi apps/server/src/persistence/Layers/ProjectionMagi.test.ts apps/server/src/persistence/Migrations/055_MagiProjections.test.ts apps/server/src/mcp/MagiMcpRouting.test.ts apps/server/src/provider/ProviderMagiConformance.test.ts apps/server/src/provider/ProviderMagiProfile.test.ts packages/contracts/src/magi.test.ts packages/client-runtime/src/state/magi.test.ts apps/web/src/components/magi apps/web/src/components/settings/MagiSettingsPanel.environment.test.tsx apps/web/src/components/settings/magiSettingsSaveScheduling.test.ts apps/mobile/src/features/threads/MagiPanelSheet.logic.test.ts apps/mobile/src/features/threads/magiParticipantIds.test.ts
• git diff --check base/main...HEAD

Integrated web and mobile verification and before/after UI evidence are still pending. This PR publishing pass changed no implementation files.

🤖 Generated by GPT-6 in Codex via T3 Code