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/agentStore.ts

@@ -137,9 +137,18 @@ export const useAgentStore = create<AgentStore>((set, get) => ({
 
   // Actions
   loadClones: async () => {
-    const client = getClient();
+    let client = getClient();
+
+    // Retry up to 3 times with short delay if client isn't ready yet.
+    // This handles the race where connected fires before coordinator
+    // injects the client into the store.
+    for (let attempt = 0; attempt < 3 && !client; attempt++) {
+      await new Promise((r) => setTimeout(r, 300));
+      client = getClient();
+    }
+
     if (!client) {
-      log.warn('[AgentStore] Client not initialized, skipping loadClones');
+      log.warn('[AgentStore] Client not initialized after retries, skipping loadClones');
       return;
     }