feat: subagent summon — catalog filter, error hints, system prompt, AgentBuilder default, SubAgent mode display

- Filter summon tool catalog to is_subagent-flagged agents only
- Return fresh subagent list in error when slug not found
- Add subagent hint to system prompt when summon tool available
- Default is_subagent checkbox to true in AgentBuilder
- Fix tab-created event to include agentSlug and agentModels
- Add SubAgent read-only mode to ModelSelector with model slider

2 files changed, 18 insertions, 14 deletions

diff --git a/packages/core/src/tools/summon.ts b/packages/core/src/tools/summon.ts
index ed4b080..34109f3 100644
--- a/packages/core/src/tools/summon.ts
+++ b/packages/core/src/tools/summon.ts
@@ -215,18 +215,20 @@ export function toAvailableAgents(
 	globalDir: string,
 	projectDir: string | null,
 ): AvailableAgent[] {
-	return defs.map((d) => {
-		const baseDir =
-			d.scope === "global"
-				? globalDir
-				: projectDir
-					? `${projectDir.replace(/\/$/, "")}/.dispatch/agents`
-					: globalDir;
-		return {
-			slug: d.slug,
-			name: d.name,
-			description: d.description,
-			path: `${baseDir}/${d.slug}.toml`,
-		};
-	});
+	return defs
+		.filter((d) => d.is_subagent)
+		.map((d) => {
+			const baseDir =
+				d.scope === "global"
+					? globalDir
+					: projectDir
+						? `${projectDir.replace(/\/$/, "")}/.dispatch/agents`
+						: globalDir;
+			return {
+				slug: d.slug,
+				name: d.name,
+				description: d.description,
+				path: `${baseDir}/${d.slug}.toml`,
+			};
+		});
 }
diff --git a/packages/core/src/types/index.ts b/packages/core/src/types/index.ts
index 0df56ca..4148498 100644
--- a/packages/core/src/types/index.ts
+++ b/packages/core/src/types/index.ts
@@ -149,7 +149,9 @@ export type AgentEvent =
 			keyId: string | null;
 			modelId: string | null;
 			parentTabId: string | null;
+			agentSlug?: string | null;
 			workingDirectory: string | null;
+			agentModels?: Array<{ key_id: string; model_id: string }> | null;
 	  }
 	| { type: "message-queued"; tabId: string; messageId: string; message: string }
 	| { type: "message-consumed"; tabId: string; messageIds: string[] }