feat(ws): handle conversation.open broadcast — open/focus tab from CLI --open

Consume the conversation.open handoff ([email protected], [email protected]).
Re-pinned file: deps + re-mirrored .dispatch/*.reference.md.

- WS adapter (logic.ts + index.ts): parse + route the new top-level
  "conversation.open" WsServerMessage to an onConversationOpen handler
- app store: openConversation(id) opens (or focuses) a tab — creates a chat
  store, loads history, subscribes to live turns, creates+selects the tab
- conformance guard + WS adapter tests cover the new type
- backend also shipped conversation metadata endpoints (GET /conversations,
  GET /conversations/:id/last, GET/PUT /conversations/:id/title) — mirrored
  but not yet consumed by the FE

682 tests green.

1 files changed, 23 insertions, 8 deletions

diff --git a/backend-handoff.md b/backend-handoff.md
index 5b54f2d..64147ff 100644
--- a/backend-handoff.md
+++ b/backend-handoff.md
@@ -5,18 +5,32 @@
 > **From:** dispatch-web orchestrator · **To:** arch-rewrite orchestrator · **Courier:** the user.
 > `lsp` does NOT span the repos (AGENTS.md § Backend seam) — every cross-repo ask flows through here.
 
-_Last updated: 2026-06-21 (message-queue + steering handoff consumed). **FE is current on
-`[email protected]` / `[email protected]` / `[email protected]`.** All handoffs to date are
+_Last updated: 2026-06-21 (conversation.open handoff consumed). **FE is current on
+`[email protected]` / `[email protected]` / `[email protected]`.** All handoffs to date are
 consumed: surfaces + WS, conversation transcript/metrics, tabs + model selector, cache-warming
 (incl. authoritative timer + retention + cache-rate fix + the CR-4 lifecycle below),
 **per-conversation cwd + LSP status**, **context size**, **turn continuity + multi-client live
 view**, the **chat limit + CR-5 history windowing**, the **reasoning effort
-(thinking-depth knob)**, and the **message queue + steering** (below).
+(thinking-depth knob)**, the **message queue + steering**, the **todo task list**, and the
+**conversation.open broadcast** (below).
 **Open asks: NONE.** CR-1/CR-2/CR-4/CR-5 all RESOLVED ✅ (see §2); §3 lists likely next asks.
 **CR-3 (watcher couldn't see the USER prompt until seal) → RESOLVED ✅** — backend shipped the
 `user-message` turn event; FE re-pinned + consumption live.
 The cwd/LSP draft-path verification (`backend-handoff-cwd-lsp.md`) came back **all ✅ confirmed**._
 
+**Conversation.open handoff (`frontend-conversation-open-handoff.md`) → CONSUMED ✅.**
+Re-pinned `[email protected]→0.9.0` + `[email protected]→0.13.0` (`ui-contract` unchanged);
+re-mirrored both `.dispatch/*.reference.md`. FE work: the WS adapter (`adapters/ws/logic.ts` +
+`index.ts`) parses + routes the new `"conversation.open"` top-level `WsServerMessage` to an
+`onConversationOpen` handler; the app store's `openConversation(conversationId)` opens (or
+focuses) a tab for the broadcast conversation — if not already open, creates a chat store,
+loads history, subscribes to live turns, creates the tab; then selects it + refreshes
+cwd/effort/surfaces. The conformance guard + WS adapter tests cover the new type. The backend
+also shipped conversation metadata endpoints (`GET /conversations`, `GET /conversations/:id/last`,
+`GET`/`PUT /conversations/:id/title`, `POST /conversations/:id/open`) — NOT yet consumed by the FE
+(mirrored for reference; wire when a conversation picker/list UI is built). 682 tests green. NO
+new backend ask._
+
 **Message-queue + steering handoff (`frontend-message-queue-handoff.md`) → CONSUMED ✅.**
 Re-pinned `[email protected]→0.8.0` + `[email protected]→0.12.0` (`ui-contract` unchanged —
 the queue uses the existing `custom` surface field kind); re-mirrored both
@@ -101,13 +115,13 @@ backend ask — but the max-limit denominator is now a live FE need; see §3.
 
 ## 1. Pinned backend contracts (consumed by the FE)
 
-Pinned as `file:` deps: **`[email protected]`; `[email protected]`; `[email protected]`**.
+Pinned as `file:` deps: **`[email protected]`; `[email protected]`; `[email protected]`**.
 
 | Package | Used for |
 |---|---|
 | `@dispatch/ui-contract` | surfaces + surface WS protocol |
-| `@dispatch/wire` | `Chunk`/`StoredChunk`(+`seq`)/`ChatMessage`/`AgentEvent`/`TurnSealedEvent`/`Usage`/`StepId` + metrics: `StepMetrics`/`TurnMetrics`, `usage.stepId`, `step-complete`, `done.durationMs`/`done.usage`, `tool-result.durationMs`, **`done.contextSize`/`TurnMetrics.contextSize`**, **`ReasoningEffort`**, **`QueuedMessage`/`QueuePayload`/`TurnSteeringEvent`** |
-| `@dispatch/transport-contract` | `ChatRequest`(+`reasoningEffort`)/`ModelsResponse`/`ConversationHistoryResponse`/`ConversationMetricsResponse` + `WarmRequest`/`WarmResponse` + `CwdResponse`/`SetCwdRequest` + `ReasoningEffortResponse`/`SetReasoningEffortRequest` + **`QueueRequest`/`QueueResponse`/`ChatQueueMessage`** + LSP (`LspStatusResponse`/`LspServerInfo`/`LspServerState`) + WS chat ops + `WsClientMessage`/`WsServerMessage` |
+| `@dispatch/wire` | `Chunk`/`StoredChunk`(+`seq`)/`ChatMessage`/`AgentEvent`/`TurnSealedEvent`/`Usage`/`StepId` + metrics: `StepMetrics`/`TurnMetrics`, `usage.stepId`, `step-complete`, `done.durationMs`/`done.usage`, `tool-result.durationMs`, **`done.contextSize`/`TurnMetrics.contextSize`**, **`ReasoningEffort`**, **`QueuedMessage`/`QueuePayload`/`TurnSteeringEvent`**, **`ConversationMeta`** |
+| `@dispatch/transport-contract` | `ChatRequest`(+`reasoningEffort`)/`ModelsResponse`/`ConversationHistoryResponse`/`ConversationMetricsResponse` + `WarmRequest`/`WarmResponse` + `CwdResponse`/`SetCwdRequest` + `ReasoningEffortResponse`/`SetReasoningEffortRequest` + **`QueueRequest`/`QueueResponse`/`ChatQueueMessage`** + **`ConversationOpenMessage`/`ConversationListResponse`/`LastMessageResponse`/`OpenConversationResponse`/`SetTitleRequest`/`TitleResponse`** + LSP (`LspStatusResponse`/`LspServerInfo`/`LspServerState`) + WS chat ops + `WsClientMessage`/`WsServerMessage` |
 
 Endpoints in use (HTTP **24203**, WS **24205**, CORS `*` incl. `PUT`):
 `POST /chat` (NDJSON) · `GET /models` ·
@@ -118,11 +132,12 @@ Endpoints in use (HTTP **24203**, WS **24205**, CORS `*` incl. `PUT`):
 tab-close: abort turn + stop/disable warming) · **`POST /conversations/:id/queue`** (enqueue
 steering message; auto-starts a turn if idle) · WS `chat.send`→`chat.delta` ·
 WS `chat.subscribe`/`chat.unsubscribe` (watch a conversation's turns without sending; replay + live) ·
-**WS `chat.queue`** (enqueue steering; fire-and-forget — surface updates on success).
+**WS `chat.queue`** (enqueue steering; fire-and-forget — surface updates on success) ·
+**WS `conversation.open`** (broadcast: CLI `--open` flag signals the FE to open/focus a tab).
 
 Mirrored in-repo for headless agents: `.dispatch/{ui-contract,wire,transport-contract}.reference.md`
 (regenerate on any contract bump; all current as of `[email protected]` /
-`[email protected]` / `[email protected]`).
+`[email protected]` / `[email protected]`).
 
 ## 2. Open asks FOR THE BACKEND