fix(desktop): resolve all remaining P1 defects (P1-02/05/06, P1-01 experimental)

- P1-02: Heartbeat auto-initialized in kernel_init for default agent
- P1-05: CloneManager shows warning when deleting active agent + auto-switch
- P1-06: AgentInfo returns soul/system_prompt/temperature/max_tokens
- P1-01: Browser Hand marked experimental (requires Fantoccini bridge)
- Updated DEFECT_LIST.md: all P1 resolved (0 active)
- Updated RELEASE_READINESS.md: all P1 sections reflect current status

desktop/src/lib/kernel-types.ts

@@ -29,6 +29,10 @@ export interface AgentInfo {
   messageCount: number;
   createdAt: string;
   updatedAt: string;
+  soul?: string;
+  systemPrompt?: string;
+  temperature?: number;
+  maxTokens?: number;
 }
 
 export interface CreateAgentRequest {