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/views/PlanView.tsx

@@ -29,6 +29,7 @@ import { useFeatureFlagsStore } from '@/stores/useFeatureFlagsStore';
 import { useProjectsStore } from '@/stores/useProjectsStore';
 import { useSelectionStore } from '@/sync/selection-store';
 import { useConfigStore } from '@/stores/useConfigStore';
+import { useSessionGoalArmStore } from '@/stores/useSessionGoalArmStore';
 import { useUIStore } from '@/stores/useUIStore';
 import { useGitStore } from '@/stores/useGitStore';
 import { useRuntimeAPIs } from '@/hooks/useRuntimeAPIs';
@@ -594,6 +595,19 @@ export const PlanView: React.FC<PlanViewProps> = ({ targetPath = null }) => {
         }
 
         setCurrentSession(sessionId, directoryHint);
+        // "Run as goal" rides the same arm mechanism as the composer target
+        // button; set explicitly either way so a stray armed flag cannot
+        // leak into a non-goal plan send. The objective override carries the
+        // actual plan content — "Implement this plan: X" alone would give
+        // the progress audit nothing to judge against.
+        const goalObjective = execution.runAsGoal === true
+          ? [
+              `Implement the plan "${sendPromptTitle}" end-to-end${resolvedPath ? ` (plan file: ${resolvedPath})` : ''}.`,
+              '',
+              content,
+            ].join('\n')
+          : null;
+        useSessionGoalArmStore.getState().setArmed(execution.runAsGoal === true, goalObjective);
         await sendMessage(
           visiblePrompt,
           execution.providerID,
@@ -610,7 +624,7 @@ export const PlanView: React.FC<PlanViewProps> = ({ targetPath = null }) => {
         setIsPlanSendSubmitting(false);
       }
     },
-    [canCreateWorktree, createSession, currentProjectRef, initializeNewOpenChamberSession, pendingPlanSend, resolvedPath, routeToChat, sendMessage, sendPromptTitle, setCurrentSession]
+    [canCreateWorktree, content, createSession, currentProjectRef, initializeNewOpenChamberSession, pendingPlanSend, resolvedPath, routeToChat, sendMessage, sendPromptTitle, setCurrentSession]
   );
 
   const blockWidgets = React.useMemo(() => {
@@ -778,6 +792,7 @@ export const PlanView: React.FC<PlanViewProps> = ({ targetPath = null }) => {
         target={pendingPlanSend?.target ?? 'session'}
         projectDirectory={currentProjectRef?.path ?? null}
         submitting={isPlanSendSubmitting}
+        allowRunAsGoal
         onConfirm={handleConfirmPlanSend}
       />