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/components/session/sidebar/SessionNodeItem.tsx

@@ -34,6 +34,8 @@ import { useSessionUnseenCount } from '@/sync/notification-store';
 import { useSessionMultiSelectStore } from '@/stores/useSessionMultiSelectStore';
 import { useI18n } from '@/lib/i18n';
 import { useShiftKeyHeld } from '@/hooks/useShiftKeyHeld';
+import { getSessionGoal } from '@/lib/sessionGoalMetadata';
+import { sessionGoalStatusColor, sessionGoalStatusLabelKey } from '@/lib/sessionGoalPresentation';
 import { getRuntimeBearerTokenSync } from '@/lib/runtime-auth';
 import { getRuntimeApiBaseUrl } from '@/lib/runtime-switch';
 import { parseMultiRunSessionTitle } from '@/lib/multirun/title';
@@ -353,6 +355,16 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
   );
   const sessionStatus = useGlobalSessionStatus(session.id);
   const sessionPermissions = useSessionPermissions(session.id, sessionDirectory ?? undefined);
+  const sessionGoal = getSessionGoal(resolvedSession);
+  const sessionGoalGlyph = sessionGoal ? (
+    <span
+      className="inline-flex flex-shrink-0 items-center"
+      title={t(sessionGoalStatusLabelKey[sessionGoal.status] as never)}
+      aria-label={t(sessionGoalStatusLabelKey[sessionGoal.status] as never)}
+    >
+      <Icon name="target" className="h-3 w-3" style={{ color: sessionGoalStatusColor[sessionGoal.status] }} />
+    </span>
+  ) : null;
   const isActive = currentSessionId === session.id;
   const sessionTitle = resolvedSession.title || t('sessions.sidebar.session.untitled');
   const hasChildren = node.children.length > 0;
@@ -1030,15 +1042,21 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
                   >
                     <div className={cn('flex w-full items-center min-w-0 flex-1 overflow-hidden', isMinimalMode ? 'gap-1' : 'gap-1')}>
                       <div className={cn('block min-w-0 flex-1 truncate typography-ui-label font-normal', isActive ? 'text-primary' : 'text-foreground')}>{renderHighlightedText(sessionTitle, normalizedSessionSearchQuery)}</div>
-                      {alwaysShowActions ? <span className="ml-2 flex-shrink-0 text-[0.72rem] text-muted-foreground/75">{sessionCompactUpdatedLabel}</span> : null}
+                      {alwaysShowActions ? (
+                        <span className="ml-2 inline-flex flex-shrink-0 items-center gap-1 text-[0.72rem] text-muted-foreground/75">
+                          {sessionGoalGlyph}
+                          {sessionCompactUpdatedLabel}
+                        </span>
+                      ) : null}
                       {!alwaysShowActions ? (
                         <div className="relative ml-1 flex h-4 min-w-4 flex-shrink-0 items-center justify-end">
                           <span className={cn(
-                            'whitespace-nowrap text-right text-[0.72rem] text-muted-foreground/75 transition-opacity duration-150',
+                            'inline-flex items-center gap-1 whitespace-nowrap text-right text-[0.72rem] text-muted-foreground/75 transition-opacity duration-150',
                             isSessionMenuOpen
                               ? 'opacity-0'
                               : hideOnHoverClass,
                           )}>
+                            {sessionGoalGlyph}
                             {sessionCompactUpdatedLabel}
                           </span>
                         </div>
@@ -1105,6 +1123,7 @@ function SessionNodeItemComponent(props: Props): React.ReactNode {
                 {!isMinimalMode ? (
                   <div className="flex items-center justify-between gap-3 text-muted-foreground/60 min-w-0 overflow-hidden leading-tight" style={{ fontSize: 'calc(var(--text-ui-label) * 0.85)' }}>
                     <div className={cn('flex min-w-0 items-center gap-1.5 overflow-hidden', metadataSubsessionChevron && hasChildren ? 'pl-4' : '')}>
+                      {sessionGoalGlyph}
                       <span className="flex-shrink-0">{sessionUpdatedLabel}</span>
                       {hasSecondaryProjectLabel ? <span className="truncate">{secondaryMeta?.projectLabel}</span> : null}
                       {hasSecondaryBranchLabel ? <span className="inline-flex min-w-0 items-center gap-0.5"><Icon name="git-branch" className="h-3 w-3 flex-shrink-0 text-muted-foreground/70" /><span className="truncate">{secondaryMeta?.branchLabel}</span></span> : null}