fix: simplify persona resolution to single path, use personaDesc for system prompt

server/hooks.go

@@ -197,34 +197,24 @@ 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
-    //   KV "custom" or dropdown "custom" → use CustomPersona textarea field
-    //   Otherwise → resolve from personaLibrary
+    //   "custom" → CustomPersona textarea (falls back to defaultCustomPersona if empty)
+    //   otherwise → resolve from personaLibrary
     persona := p.GetPersonaOverride(post.UserId, post.ChannelId)
+    if persona == "" {
+        persona = cfg.Persona
+    }
+    var personaDesc string
     if persona == "custom" {
-        persona = cfg.CustomPersona
-        if persona == "" {
-            persona = defaultCustomPersona
+        personaDesc = cfg.CustomPersona
+        if personaDesc == "" {
+            personaDesc = defaultCustomPersona
         }
     } else {
-        persona = resolvePersona(persona)
-    }
-    if persona == "" {
-        if cfg.Persona == "custom" {
-            persona = cfg.CustomPersona
-            if persona == "" {
-                persona = defaultCustomPersona
-            }
-        } else {
-            persona = resolvePersona(cfg.Persona)
-            // If resolvePersona returned empty but a value was set, use it as-is (legacy fallback).
-            if persona == "" && cfg.Persona != "" {
-                persona = cfg.Persona
-            }
-        }
+        personaDesc = resolvePersona(persona)
     }
     systemPrompt := ""
-    if persona != "" {
-        systemPrompt = "You are " + persona + ". Respond in character. Only respond to the latest message — do not re-address earlier messages. Vary your openings and phrasing each time."
+    if personaDesc != "" {
+        systemPrompt = "You are " + personaDesc + ". Respond in character. Only respond to the latest message — do not re-address earlier messages. Vary your openings and phrasing each time."
         if cfg.Brevity != "" && cfg.Brevity != "0" {
             systemPrompt += " Reply in " + cfg.Brevity + " sentences or fewer."
         }