refactor(background-agent): normalize task ID field naming

Rename BackgroundTask and attempt ID fields to camelCase across background-agent consumers while moving BackgroundManager construction to a single config object.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

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

@@ -97,7 +97,7 @@ Task ID: ${task.id}
 Description: ${task.description}
 Agent: ${task.agent}
 Status: ${task.status}
-Session ID: ${task.sessionID ?? "N/A"}
+Session ID: ${task.sessionId ?? "N/A"}
 
 Thinking summary (first ${THINKING_SUMMARY_MAX_CHARS} chars):
 ${summaryText}

src/hooks/unstable-agent-babysitter/unstable-agent-babysitter-hook.ts

@@ -203,7 +203,7 @@ export function createUnstableAgentBabysitterHook(ctx: BabysitterContext, option
       const lastReminderAt = reminderCooldowns.get(task.id)
       if (lastReminderAt && now - lastReminderAt < COOLDOWN_MS) continue
 
-      const summary = task.sessionID ? await getThinkingSummary(ctx, task.sessionID) : null
+      const summary = task.sessionId ? await getThinkingSummary(ctx, task.sessionId) : null
       const reminder = buildReminder(task, summary, idleMs)
       const { agent, model, tools } = await resolveMainSessionTarget(ctx, mainSessionID)