refactor(hooks): split session-notification and unstable-agent-babysitter

Extract notification and babysitter logic:
- session-notification-formatting.ts, session-notification-scheduler.ts
- session-notification-sender.ts, session-todo-status.ts
- task-message-analyzer.ts: message analysis for babysitter hook

src/hooks/unstable-agent-babysitter/task-message-analyzer.ts

@@ -0,0 +1,91 @@
+import type { BackgroundTask } from "../../features/background-agent"
+
+export const THINKING_SUMMARY_MAX_CHARS = 500 as const
+
+type MessageInfo = {
+  role?: string
+  agent?: string
+  model?: { providerID: string; modelID: string }
+  providerID?: string
+  modelID?: string
+}
+
+type MessagePart = {
+  type?: string
+  text?: string
+  thinking?: string
+}
+
+function hasData(value: unknown): value is { data?: unknown } {
+  return typeof value === "object" && value !== null && "data" in value
+}
+
+function isRecord(value: unknown): value is Record<string, unknown> {
+  return typeof value === "object" && value !== null
+}
+
+export function getMessageInfo(value: unknown): MessageInfo | undefined {
+  if (!isRecord(value)) return undefined
+  if (!isRecord(value.info)) return undefined
+  const info = value.info
+  const modelValue = isRecord(info.model)
+    ? info.model
+    : undefined
+  const model = modelValue && typeof modelValue.providerID === "string" && typeof modelValue.modelID === "string"
+    ? { providerID: modelValue.providerID, modelID: modelValue.modelID }
+    : undefined
+  return {
+    role: typeof info.role === "string" ? info.role : undefined,
+    agent: typeof info.agent === "string" ? info.agent : undefined,
+    model,
+    providerID: typeof info.providerID === "string" ? info.providerID : undefined,
+    modelID: typeof info.modelID === "string" ? info.modelID : undefined,
+  }
+}
+
+export function getMessageParts(value: unknown): MessagePart[] {
+  if (!isRecord(value)) return []
+  if (!Array.isArray(value.parts)) return []
+  return value.parts.filter(isRecord).map((part) => ({
+    type: typeof part.type === "string" ? part.type : undefined,
+    text: typeof part.text === "string" ? part.text : undefined,
+    thinking: typeof part.thinking === "string" ? part.thinking : undefined,
+  }))
+}
+
+export function extractMessages(value: unknown): unknown[] {
+  if (Array.isArray(value)) {
+    return value
+  }
+  if (hasData(value) && Array.isArray(value.data)) {
+    return value.data
+  }
+  return []
+}
+
+export function isUnstableTask(task: BackgroundTask): boolean {
+  if (task.isUnstableAgent === true) return true
+  const modelId = task.model?.modelID?.toLowerCase()
+  return modelId ? modelId.includes("gemini") || modelId.includes("minimax") : false
+}
+
+export function buildReminder(task: BackgroundTask, summary: string | null, idleMs: number): string {
+  const idleSeconds = Math.round(idleMs / 1000)
+  const summaryText = summary ?? "(No thinking trace available)"
+  return `Unstable background agent appears idle for ${idleSeconds}s.
+
+Task ID: ${task.id}
+Description: ${task.description}
+Agent: ${task.agent}
+Status: ${task.status}
+Session ID: ${task.sessionID ?? "N/A"}
+
+Thinking summary (first ${THINKING_SUMMARY_MAX_CHARS} chars):
+${summaryText}
+
+Suggested actions:
+- background_output task_id="${task.id}" full_session=true include_thinking=true include_tool_results=true message_limit=50
+- background_cancel taskId="${task.id}"
+
+This is a reminder only. No automatic action was taken.`
+}