fix: 4 pre-release bug fixes — identity override, model config, agent sync, auto-identity

P1: identity.rs get_identity() returns empty soul/instructions for agents
without explicit identity files. This prevents the default ZCLAW personality
from overriding agent_config.system_prompt. New get_identity_or_default()
method added for the DEFAULT agent.

P2: messaging.rs now uses agent_config.model.model when available, falling
back to global Kernel config. This allows per-agent model selection.

P2: agentStore.ts loadClones retries up to 3 times (300ms interval) when
getClient() returns null, handling the coordinator initialization race.

P2: agent_create Tauri command auto-populates identity files (soul +
instructions) from creation parameters, ensuring build_system_prompt()
has content for new agents.

Also fixes conversationStore upsertActiveConversation to persist generated
conversation IDs, preventing duplicate entries on new conversations.

desktop/src/store/chat/conversationStore.ts

@@ -325,11 +325,19 @@ export const useConversationStore = create<ConversationState>()(
 
   upsertActiveConversation: (currentMessages: ChatMessage[]) => {
     const state = get();
+    const currentId = state.currentConversationId || null;
     const conversations = upsertActiveConversation(
       [...state.conversations], currentMessages, state.sessionKey,
       state.currentConversationId, state.currentAgent,
     );
-    set({ conversations });
+    // If this was a new conversation (no prior currentConversationId),
+    // persist the generated ID so subsequent upserts update in-place
+    // instead of creating duplicate entries.
+    if (!currentId && conversations.length > 0) {
+      set({ conversations, currentConversationId: conversations[0].id });
+    } else {
+      set({ conversations });
+    }
     return conversations;
   },