docs: initialize MS19 Chat & Terminal mission planning (#513)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

docs/scratchpads/ms19-chat-terminal-20260225.md

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+# Mission Scratchpad — MS19 Chat & Terminal System
+
+> Append-only log. NEVER delete entries. NEVER overwrite sections.
+> This is the orchestrator's working memory across sessions.
+
+## Original Mission Prompt
+
+```
+Plan MS19+, update mission artifacts for Coolify → Portainer transition.
+MS18 is complete. Coolify deprecated, Portainer migration in progress with another agent.
+```
+
+## Planning Decisions
+
+### 2026-02-25 — Infrastructure Assessment
+
+**Existing chat infrastructure (~95% complete):**
+
+- ChatOverlay.tsx, ConversationSidebar.tsx, ChatInput.tsx, MessageList.tsx
+- useChat hook with conversation management and LLM interaction
+- Backend LLM controller with SSE streaming support
+- Providers: Ollama, Claude, OpenAI
+- Chat persistence via Ideas API
+
+**Existing terminal infrastructure (UI-only):**
+
+- TerminalPanel.tsx with tabs, rich output styling, animations
+- No backend connection — purely mock UI
+
+**Existing orchestrator infrastructure:**
+
+- Orchestrator service (NestJS, port 3002) with agent spawn/kill/status
+- SSE stream at /agents/events for real-time agent status
+- Web proxy routes at /api/orchestrator/\*
+- Coordinator integration in API for job tracking
+
+**Key pattern reference:**
+
+- Speech gateway (`apps/api/src/speech/speech.gateway.ts`) shows namespace WebSocket pattern with session management
+
+### 2026-02-25 — Architecture Decisions
+
+**Decision: node-pty for terminal backend**
+
+- Standard PTY management for Node.js (used by VS Code)
+- Spawns real shell processes (bash/zsh)
+- Handles resize, input/output streams
+- WebSocket namespace /terminal for communication
+
+**Decision: Terminal sessions in PostgreSQL**
+
+- Consistent with workspace isolation pattern
+- Prisma model: TerminalSession (id, workspaceId, name, status, createdAt, closedAt)
+- Sessions survive page reload, recover on reconnect
+
+**Decision: SSE for chat streaming (not WebSocket)**
+
+- Backend already has SSE setup in LLM controller
+- Only frontend wiring missing (streamChatMessage() is TODO)
+- SSE is simpler and sufficient for unidirectional token streaming
+
+**Decision: Orchestrator commands as chat prefixes**
+
+- /spawn, /status, /jobs, /kill parsed in frontend
+- Route through existing /api/orchestrator/\* proxy
+- Display structured responses inline in chat
+
+### 2026-02-25 — Portainer Migration
+
+**Context:** Coolify has been deprecated and shut down. Infrastructure migration to Portainer is being handled by another agent. All deployment references updated from Coolify to Portainer in PRD and mission manifest.
+
+**Impact on MS19:**
+
+- Deployment target is now Portainer (was Coolify)
+- No code changes needed — only infrastructure config
+- Smoke testing blocked until Portainer stack is running
+
+## Session Log
+
+### S1 — 2026-02-25
+
+- Read mission state (MS18 complete, all 16 tasks done)
+- Explored codebase for MS19 infrastructure (chat, terminal, WebSocket, orchestrator)
+- Updated PRD: Coolify → Portainer, added MS18 completion, added MS19 FRs and acceptance criteria
+- Created new MISSION-MANIFEST.md for MS19+ mission
+- Created TASKS.md with 12-task breakdown (~250K token estimate)
+- Created this scratchpad
+- Archived MS18 TASKS.md to docs/tasks/MS18-ThemeWidgets-tasks.md