fix: plugin bot user + await plugin detection before session scan

- Add EnsureBotUser on plugin activate (fixes 'Unable to find user' error)
- Accept bot_user_id in create session request
- Await plugin health check before starting session monitor
  (prevents race where sessions detect before plugin flag is set)
- Plugin now creates custom_livestatus posts with proper bot user

plugin/server/plugin.go

@@ -3,6 +3,7 @@ package main
 import (
 	"sync"
 
+	"github.com/mattermost/mattermost/server/public/model"
 	"github.com/mattermost/mattermost/server/public/plugin"
 )
 
@@ -18,16 +19,37 @@ type Plugin struct {
 
 	// store wraps KV store operations for session persistence.
 	store *Store
+
+	// botUserID is the plugin's bot user ID (created on activation).
+	botUserID string
 }
 
 // OnActivate is called when the plugin is activated.
 func (p *Plugin) OnActivate() error {
 	p.store = NewStore(p.API)
 
+	// Ensure plugin bot user exists
+	botID, appErr := p.API.EnsureBotUser(&model.Bot{
+		Username:    "livestatus",
+		DisplayName: "Live Status",
+		Description: "OpenClaw Live Status plugin bot",
+	})
+	if appErr != nil {
+		p.API.LogWarn("Failed to ensure bot user", "error", appErr.Error())
+	} else {
+		p.botUserID = botID
+		p.API.LogInfo("Plugin bot user ensured", "botUserID", botID)
+	}
+
 	p.API.LogInfo("OpenClaw Live Status plugin activated")
 	return nil
 }
 
+// getBotUserID returns the plugin's bot user ID.
+func (p *Plugin) getBotUserID() string {
+	return p.botUserID
+}
+
 // OnDeactivate is called when the plugin is deactivated.
 func (p *Plugin) OnDeactivate() error {
 	// Mark all active sessions as interrupted