feat(opencode): add order field to agent config for explicit list sorting

Adds an optional order field to Agent.Info and ConfigAgent.Info schemas so users
and plugins can control agent display order. Sort precedence: order (asc),
default_agent (desc), name (asc).

Author: zir

packages/opencode/src/agent/agent.ts

@@ -45,6 +45,7 @@ export const Info = z
     prompt: z.string().optional(),
     options: z.record(z.string(), z.any()),
     steps: z.number().int().positive().optional(),
+    order: z.number().int().optional(),
   })
   .meta({
     ref: "Agent",
@@ -258,6 +259,7 @@ export const layer = Layer.effect(
           item.hidden = value.hidden ?? item.hidden
           item.name = value.name ?? item.name
           item.steps = value.steps ?? item.steps
+          item.order = value.order ?? item.order
           item.options = mergeDeep(item.options, value.options ?? {})
           item.permission = Permission.merge(item.permission, Permission.fromConfig(value.permission ?? {}))
         }
@@ -288,6 +290,7 @@ export const layer = Layer.effect(
             agents,
             values(),
             sortBy(
+              [(x) => x.order ?? Number.MAX_SAFE_INTEGER, "asc"],
               [(x) => (cfg.default_agent ? x.name === cfg.default_agent : x.name === "build"), "desc"],
               [(x) => x.name, "asc"],
             ),

packages/opencode/src/config/agent.ts

@@ -47,6 +47,7 @@ export const Info = z
       .describe("Maximum number of agentic iterations before forcing text-only response"),
     maxSteps: z.number().int().positive().optional().describe("@deprecated Use 'steps' field instead."),
     permission: ConfigPermission.Info.optional(),
+    order: z.number().int().optional().describe("Display order in the agent list. Lower values appear first."),
   })
   .catchall(z.any())
   .transform((agent, _ctx) => {
@@ -67,6 +68,7 @@ export const Info = z
       "permission",
       "disable",
       "tools",
+      "order",
     ])
 
     const options: Record<string, unknown> = { ...agent.options }