Add LlmInputSnapshot interface tracking systemPrompt/userMessage/messages/conversationHistory/updatedAt/attempt, store lastLlmInputSnapshot in Brain and inject into RuntimeGlobals as llmInput, expose llmInput/llmMessages/llmSystemPrompt/llmUserMessage/llmConversationHistory as frozen readonly globals in JavaScriptPlanner sandbox, add source:'manual'|'llm' field to DebugReplResult to distinguish user-triggered vs autonomous