Fix notifications opening the wrong workspace (#2331)

* fix(app): open notifications on the right host

Agent notifications previously omitted workspace ownership, so a cold target host was treated as missing and fell back to its empty home route. Carry the authoritative workspace and keep older notifications on a target-host resolver until lookup is conclusive.

* fix(app): separate notification and agent URL routing

Notifications use their authoritative workspace target directly. Stable agent URLs remain server-and-agent targets whose workspace is resolved by the agent route.

* fix(protocol): preserve notification workspace targets

Both attention message variants retain workspaceId through outbound validation so notification clicks receive the authoritative route target.

* test(app): use workspace-scoped notification target

* test(server): give notification agents workspace targets

* test(app): target notification workspace in navigation e2e

packages/protocol/src/messages.ts

@@ -658,6 +658,7 @@ export const AgentStreamEventPayloadSchema = z.discriminatedUnion("type", [
         body: z.string(),
         data: z.object({
           serverId: z.string(),
+          workspaceId: z.string().optional(),
           agentId: z.string(),
           reason: z.enum(["finished", "error", "permission"]),
         }),
@@ -3564,6 +3565,7 @@ export const AgentAttentionRequiredMessageSchema = z.object({
         body: z.string(),
         data: z.object({
           serverId: z.string(),
+          workspaceId: z.string().optional(),
           agentId: z.string(),
           reason: z.enum(["finished", "error", "permission"]),
         }),