feat: session goals - server-driven goal loop with independent small-model audit (#2148)

Arm the target button in the composer and the next prompt becomes a goal:
the server keeps the session working toward it (idle tick -> small-model
audit -> continuation) until the objective is verifiably complete, blocked,
or out of budget — even with the UI closed.

Server (packages/web/server/lib/session-goal):
- event-driven loop on the global SSE hub; goal state lives in
  session.metadata.openchamber.goal (merge-safe patches, stale-write guard
  by goal id), so it survives restarts and syncs to every client for free
- the small-model audit (objective + last assistant turn only, language
  pinned to the objective) is the sole termination authority; blocked needs
  3 consecutive verdicts, audit outages tolerate one unaudited continuation
  then stop the goal as resumable-blocked
- hard stops: optional token budget, auto-continuation cap (Resume grants a
  fresh allowance), turn errors; user abort pauses the goal instead of
  blocking it, and resuming over an aborted tail nudges immediately
- token accounting as a snapshot of the latest turn (input + cache.read +
  output), goal-relative via a creation baseline and segmented across
  compactions; a compaction summary skips the audit and continues
- continuations reuse the session's own provider/model/agent/variant

UI:
- three-mode target button (arm / disarm / manage dialog), informational
  goal strip with inline pause/resume and an Evaluating indicator, sidebar
  state glyph, objective length counter (2000-char server clamp),
  read-only completed goals
- goal entry points: composer (sessions and drafts), start-new-session-
  from-answer dialog, plan implement dialog (plan content becomes the
  objective), scheduled tasks (Run as goal + budget)
- Settings -> Chat -> Goal: feature toggle + default token budget with
  three-layer parity (web server, client persistence, VS Code bridge);
  VS Code renders goal state but hides the entry points (the loop runs in
  the web server only)

Notifications: per-turn "ready" notifications are suppressed while a goal
is active; settling sends one final notification (desktop, web-push, APNs
generic titles with the session name as body) honoring the completion
toggle. Error/question/permission notifications are untouched.

Docs: user guide (session-goals) in all 9 locales + sidebar entry,
scheduled-tasks cross-reference, server module DOCUMENTATION.md.

packages/ui/src/lib/i18n/messages/ko.settings.ts

@@ -1727,6 +1727,12 @@ export const settingsDict = {
   'settings.openchamber.visual.field.sessionRecapAria': '에이전트가 완료되면 요약을 생성합니다',
   'settings.openchamber.visual.field.sessionSuggestion': '다음 사용자 메시지 제안 생성',
   'settings.openchamber.visual.field.sessionSuggestionAria': '에이전트가 완료되면 다음 사용자 메시지 제안을 생성합니다',
+  'settings.openchamber.visual.field.sessionGoal': '세션 목표 사용',
+  'settings.openchamber.visual.field.sessionGoalAria': '세션이 목표를 향해 자동으로 계속 작업하도록 합니다',
+  'settings.openchamber.visual.goal.sectionTitle': '목표',
+  'settings.openchamber.visual.goal.budgetLabel': '기본 토큰 예산',
+  'settings.openchamber.visual.goal.budgetAria': '새 목표에 기본 토큰 예산 적용',
+  'settings.openchamber.visual.goal.description': '컴포저의 타깃 버튼을 켜면 다음 메시지가 목표가 됩니다. 에이전트는 소형 모델의 감사를 받으며 자리를 비운 동안에도 자동으로 계속 작업합니다.',
   'settings.openchamber.visual.field.showReasoningTracesAria': 'Reasoning trace 표시',
   'settings.openchamber.visual.field.showReasoningTraces': 'Reasoning Trace 표시',
   'settings.openchamber.visual.field.collapsibleThinkingBlocksAria': '접을 수 있는 추론 블록 활성화',