fix: allow /ai persona custom to set KV override and use CustomPersona textarea

server/command.go

@@ -128,10 +128,12 @@ func (p *Plugin) handlePersonaList(args *model.CommandArgs) (*model.CommandRespo
 
 // handlePersonaSwitch persists a persona override for the user+channel.
 func (p *Plugin) handlePersonaSwitch(args *model.CommandArgs, personaID string) (*model.CommandResponse, *model.AppError) {
+    if personaID != "custom" {
         resolved := resolvePersona(personaID)
         if resolved == "" {
             return p.response("Unknown persona. Available: " + p.listPersonas()), nil
         }
+    }
     if err := p.SavePersonaOverride(args.UserId, args.ChannelId, personaID); err != nil {
         return p.response("Failed to save persona: " + err.Error()), nil
     }

server/hooks.go

@@ -194,10 +194,14 @@ func (p *Plugin) MessageHasBeenPosted(c *plugin.Context, post *model.Post) {
 
     // Prepend the persona system prompt to set the bot's character.
     // Priority: KV override > dropdown selection
-    //   If dropdown = "custom" → use CustomPersona textarea field
+    //   KV "custom" or dropdown "custom" → use CustomPersona textarea field
     //   Otherwise → resolve from personaLibrary
     persona := p.GetPersonaOverride(post.UserId, post.ChannelId)
+    if persona == "custom" {
+        persona = cfg.CustomPersona
+    } else {
         persona = resolvePersona(persona)
+    }
     if persona == "" {
         if cfg.Persona == "custom" {
             persona = cfg.CustomPersona