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/es.ts

@@ -293,6 +293,10 @@ export const dict: Record<I18nKey, string> = {
   "sessions.scheduledTasks.editor.prompt.placeholder": "Resumir tareas abiertas y proponer próximas acciones",
   "sessions.scheduledTasks.editor.enabled.aria": "Habilitar tarea",
   "sessions.scheduledTasks.editor.enabled.label": "Habilitado",
+  "sessions.scheduledTasks.editor.goal.label": "Ejecutar como objetivo",
+  "sessions.scheduledTasks.editor.goal.aria": "Ejecutar esta tarea como un objetivo que el agente persigue hasta completarlo",
+  "sessions.scheduledTasks.editor.goal.budgetLabel": "Presupuesto de tokens",
+  "sessions.scheduledTasks.editor.goal.budgetAria": "Limitar el objetivo a un presupuesto de tokens",
   "sessions.scheduledTasks.editor.actions.closeAria": "Cerrar",
   "sessions.scheduledTasks.editor.actions.cancel": "Cancelar",
   "sessions.scheduledTasks.editor.actions.save": "Guardar",
@@ -1389,6 +1393,39 @@ export const dict: Record<I18nKey, string> = {
   "header.actions.terminalPanelWithShortcut": "Panel de terminal ({shortcut})",
   "chat.recap.aria": "Resumen de la sesión",
   "chat.recap.label": "Resumen:",
+  "chat.goal.dialog.titleCreate": "Definir objetivo de sesión",
+  "chat.goal.dialog.titleManage": "Objetivo de sesión",
+  "chat.goal.dialog.objectiveLabel": "Objetivo",
+  "chat.goal.dialog.objectivePlaceholder": "Describe el estado final que el agente debe alcanzar y verificar…",
+  "chat.goal.dialog.budgetLabel": "Presupuesto de tokens",
+  "chat.goal.status.active": "Activo",
+  "chat.goal.status.evaluating": "Evaluando…",
+  "chat.goal.status.paused": "En pausa",
+  "chat.goal.status.blocked": "Bloqueado",
+  "chat.goal.status.budgetLimited": "Presupuesto alcanzado",
+  "chat.goal.status.complete": "Completado",
+  "chat.goal.usage.tokens": "{used} tokens",
+  "chat.goal.usage.tokensWithBudget": "{used}/{budget} tokens",
+  "chat.goal.usage.turns": "{turns} continuaciones",
+  "chat.goal.action.pause": "Pausar",
+  "chat.goal.action.resume": "Reanudar",
+  "chat.goal.action.markComplete": "Marcar como completado",
+  "chat.goal.action.clear": "Eliminar objetivo",
+  "chat.goal.action.cancel": "Cancelar",
+  "chat.goal.action.save": "Guardar objetivo",
+  "chat.goal.action.start": "Iniciar objetivo",
+  "chat.goal.toast.actionFailed": "No se pudo actualizar el objetivo",
+  "chat.goal.row.aria": "Objetivo de sesión — abrir detalles",
+  "chat.goal.button.createAria": "Definir un objetivo de sesión",
+  "chat.goal.button.manageAria": "Gestionar el objetivo de sesión",
+  "chat.goal.button.armAria": "Iniciar un objetivo con el próximo mensaje",
+  "chat.goal.counter.aria": "Límite de longitud del objetivo",
+  "chat.goal.button.disarmAria": "Objetivo armado — toca para desactivarlo",
+  "chat.goal.button.cancelAria": "Objetivo en curso — toca para cancelarlo",
+  "chat.goal.cancelDialog.title": "¿Cancelar este objetivo?",
+  "chat.goal.cancelDialog.description": "El agente dejará de trabajar automáticamente hacia este objetivo.",
+  "chat.goal.cancelDialog.keep": "Mantener objetivo",
+  "chat.goal.cancelDialog.confirm": "Cancelar objetivo",
   "chat.suggestion.applyAria": "Usar mensaje sugerido",
   "chat.suggestion.dismissAria": "Descartar sugerencia",
   "header.actions.toggleTerminalPanelAria": "Mostrar u ocultar panel de terminal",