fix(im): simplify worker bootstrap message

- remove the worker self-mention prefix from the bootstrap message
- switch the default manager image to ghcr.io/russellluo/picoclaw:2026.4.26

Author: RussellLuo

internal/config/config.go

@@ -120,7 +120,8 @@ const (
 
 	DefaultHTTPPort           = apiclient.DefaultHTTPPort
 	DefaultAccessToken        = "your_access_token"
-	DefaultManagerImage       = "opencsg-registry.cn-beijing.cr.aliyuncs.com/opencsghq/picoclaw:2026.4.24.0"
+	// Temporary default; later switch to opencsg-registry.cn-beijing.cr.aliyuncs.com/opencsghq/picoclaw.
+	DefaultManagerImage       = "ghcr.io/russellluo/picoclaw:2026.4.26"
 	CSGHubProvider            = "csghub"
 	BoxLiteSDKProvider        = "boxlite-sdk"
 	BoxLiteCLIProvider        = "boxlite-cli"

internal/im/provisioning.go

@@ -82,7 +82,7 @@ func (p *Provisioner) scheduleBootstrapMessage(roomID, name, description string)
 func buildWorkerBootstrapMessage(name, description string) string {
 	name = strings.TrimSpace(name)
 	description = strings.TrimSpace(description)
-	message := fmt.Sprintf("@%s Write this down in your memory: your name is %s.", name, name)
+	message := fmt.Sprintf("Write this down in your memory: your name is %s.", name)
 	if description == "" {
 		return message
 	}

internal/im/provisioning_test.go

@@ -62,7 +62,7 @@ func TestProvisionerEnsureAgentUserPublishesBootstrapRoom(t *testing.T) {
 	if third.Message.SenderID != "u-admin" {
 		t.Fatalf("third event.Message.SenderID = %q, want %q", third.Message.SenderID, "u-admin")
 	}
-	wantContent := "@Alice Write this down in your memory: your name is Alice. Your responsibility is test lead"
+	wantContent := "Write this down in your memory: your name is Alice. Your responsibility is test lead"
 	if third.Message.Content != wantContent {
 		t.Fatalf("third event.Message.Content = %q, want %q", third.Message.Content, wantContent)
 	}