feat(tabs): tab-to-tab agent communication via short handles

Add send_to_tab / read_tab tools so an agent can message or read another
tab by a git-style short handle (shortest unique prefix of the tab UUID,
min 4 chars), shown in the tab bar.

- core/db/tabs: resolveTabPrefix + shortestUniquePrefix (open tabs only,
  LIKE-sanitized prefix matching)
- new tools read-tab.ts / send-to-tab.ts (+ tests) decoupled from the DB
  TabRow via a minimal ResolvedTabRef projection
- agent-manager: unified deliverMessage routing (busy -> queue, idle ->
  new turn) shared by POST /chat and send_to_tab; agent->agent auto-wake
  budget (MAX_AGENT_AUTO_WAKES) to bound ping-pong loops
- summon/loader: send_to_tab + read_tab as grantable tools
- frontend: shortHandleFor + handle badge in TabBar; perm toggles
- notes: tab-comm / user-agents / todo-redesign plans
- chore: biome format fixes (debug-logger, summon.test)

Refs notes/plan-tab-comm.md

1 files changed, 15 insertions, 10 deletions

diff --git a/packages/api/src/app.ts b/packages/api/src/app.ts
index 73d3de5..19cc193 100644
--- a/packages/api/src/app.ts
+++ b/packages/api/src/app.ts
@@ -56,28 +56,33 @@ app.post("/chat", async (c) => {
 		return c.json({ error: "message must be a non-empty string" }, 400);
 	}
 
-	if (agentManager.getTabStatus(tabId) === "running") {
-		const queueId = typeof body.queueId === "string" ? body.queueId : undefined;
-		const { messageId } = agentManager.queueMessage(tabId, message, queueId);
-		return c.json({ status: "queued", messageId });
-	}
-
 	const keyId = typeof body.keyId === "string" ? body.keyId : undefined;
 	const modelId = typeof body.modelId === "string" ? body.modelId : undefined;
 	const agentModels = Array.isArray(body.agentModels) ? body.agentModels : undefined;
 	const workingDirectory =
 		typeof body.workingDirectory === "string" ? body.workingDirectory : undefined;
+	const queueId = typeof body.queueId === "string" ? body.queueId : undefined;
 	const validEfforts = ["none", "low", "medium", "high", "max"];
 	const reasoningEffort =
 		typeof body.reasoningEffort === "string" && validEfforts.includes(body.reasoningEffort)
 			? (body.reasoningEffort as "none" | "low" | "medium" | "high" | "max")
 			: undefined;
 
-	// Non-blocking — let the agent run in the background
-	agentManager
-		.processMessage(tabId, message, keyId, modelId, reasoningEffort, workingDirectory, agentModels)
-		.catch(console.error);
+	// Single routing decision (queue if busy, new turn if idle) shared with the
+	// `send_to_tab` tool via `AgentManager.deliverMessage`. Non-blocking — a
+	// started turn runs in the background.
+	const outcome = agentManager.deliverMessage(tabId, message, {
+		...(keyId ? { keyId } : {}),
+		...(modelId ? { modelId } : {}),
+		...(agentModels ? { agentModels } : {}),
+		...(reasoningEffort ? { reasoningEffort } : {}),
+		...(workingDirectory !== undefined ? { workingDirectory } : {}),
+		...(queueId ? { queueId } : {}),
+	});
 
+	if (outcome.status === "queued") {
+		return c.json({ status: "queued", messageId: outcome.messageId });
+	}
 	return c.json({ status: "ok" });
 });