perf: overhaul session loading, caching, and runtime isolation (#2360)

Improve OpenChamber responsiveness under large session workloads while fixing
cache, synchronization, and persistence correctness across runtimes, projects,
directories, and worktrees.

- prioritize selected and visible sessions during bootstrap and defer
  non-critical enrichment work
- reduce redundant message loading, event processing, store publication, and
  hidden sidebar work
- prevent stale session and message requests from overwriting newer
  authoritative state
- preserve existing data when authoritative fetches fail instead of treating
  failures as successful empty responses
- scope session materialization, messages, drafts, queues, todos, pins,
  permissions, folders, tabs, Git state, and pull request data by runtime and
  directory identity
- harden runtime switching, reconnect, cleanup, mutation reconciliation, and
  persisted-state ordering
- preserve live subagent Task linkage when metadata arrives after an older
  message request or while streaming parts are suspended
- coalesce overlapping tail refreshes without losing newer refresh demand
- improve cold-session loading by moving deferrable work out of the critical
  bootstrap path
- isolate URL authentication, mobile credentials, native secrets, and other
  runtime-owned state across endpoint changes
- bound long-lived caches and remove avoidable allocations from event and
  rendering hot paths
- limit virtualization to archive collections where it improves rendering
  without disrupting active sidebar layout
- stabilize session folders, pin ordering, expanded state, and persisted
  sidebar behavior
- open skill files through the same secure editor and outside-workspace grant
  flow used by file navigation, including worktree sessions
- expand regression coverage for stale completions, runtime collisions,
  reconnect behavior, persistence races, authoritative empty results, and
  subagent refresh ordering
- document the updated synchronization, cache ownership, performance, and
  runtime-isolation invariants

packages/ui/src/lib/i18n/messages/en.ts

@@ -1860,6 +1860,12 @@ export const dict = {
   'chat.container.returnToParent.title': 'Return to parent session',
   'chat.container.returnToParent.label': 'Parent',
   'chat.container.readOnlySubagentPromptBanner': 'Subagent sessions cannot be prompted.',
+  'chat.container.sessionLoadError.title': 'Session could not be loaded',
+  'chat.container.sessionLoadError.description': 'Check the connection and try loading this session again.',
+  'chat.container.sessionLoadError.retry': 'Try again',
+  'sessions.sidebar.group.empty.loadingSessions': 'Loading sessions…',
+  'sessions.sidebar.group.empty.loadFailed': 'Could not refresh sessions.',
+  'sessions.sidebar.group.empty.retry': 'Try again',
   'chat.unifiedControls.title': 'Controls',
   'chat.unifiedControls.model.title': 'Model',
   'chat.unifiedControls.model.noRecent': 'No recent models',

packages/ui/src/lib/i18n/messages/es.ts

@@ -1838,6 +1838,12 @@ export const dict: Record<I18nKey, string> = {
   "chat.container.returnToParent.title": "Volver a la sesión principal",
   "chat.container.returnToParent.label": "Principal",
   "chat.container.readOnlySubagentPromptBanner": "Las sesiones de subagentes no pueden recibir prompts.",
+  "chat.container.sessionLoadError.title": "No se pudo cargar la sesión",
+  "chat.container.sessionLoadError.description": "Comprueba la conexión e intenta cargar esta sesión de nuevo.",
+  "chat.container.sessionLoadError.retry": "Reintentar",
+  "sessions.sidebar.group.empty.loadingSessions": "Cargando sesiones…",
+  "sessions.sidebar.group.empty.loadFailed": "No se pudieron actualizar las sesiones.",
+  "sessions.sidebar.group.empty.retry": "Reintentar",
   "chat.unifiedControls.title": "Controles",
   "chat.unifiedControls.model.title": "Modelo",
   "chat.unifiedControls.model.noRecent": "No hay modelos recientes",

packages/ui/src/lib/i18n/messages/fr.ts

@@ -1656,6 +1656,12 @@ export const dict = {
   'chat.container.returnToParent.title': 'Retour à la session parents',
   'chat.container.returnToParent.label': 'Mère',
   'chat.container.readOnlySubagentPromptBanner': 'Les sessions de sous-agent ne peuvent pas être invitées.',
+  'chat.container.sessionLoadError.title': 'Impossible de charger la session',
+  'chat.container.sessionLoadError.description': 'Vérifiez la connexion et essayez de charger à nouveau cette session.',
+  'chat.container.sessionLoadError.retry': 'Réessayer',
+  'sessions.sidebar.group.empty.loadingSessions': 'Chargement des sessions…',
+  'sessions.sidebar.group.empty.loadFailed': 'Impossible d’actualiser les sessions.',
+  'sessions.sidebar.group.empty.retry': 'Réessayer',
   'chat.unifiedControls.title': 'Contrôles',
   'chat.unifiedControls.model.title': 'Modèle',
   'chat.unifiedControls.model.noRecent': 'Aucun modèle récent',

packages/ui/src/lib/i18n/messages/ja.ts

@@ -1856,6 +1856,12 @@ export const dict: Record<I18nKey, string> = {
   'chat.container.returnToParent.title': '親セッションに戻る',
   'chat.container.returnToParent.label': '親',
   'chat.container.readOnlySubagentPromptBanner': 'サブエージェントセッションはプロンプトを受け付けません。',
+  'chat.container.sessionLoadError.title': 'セッションを読み込めませんでした',
+  'chat.container.sessionLoadError.description': '接続を確認して、このセッションをもう一度読み込んでください。',
+  'chat.container.sessionLoadError.retry': '再試行',
+  'sessions.sidebar.group.empty.loadingSessions': 'セッションを読み込んでいます…',
+  'sessions.sidebar.group.empty.loadFailed': 'セッションを更新できませんでした。',
+  'sessions.sidebar.group.empty.retry': '再試行',
   'chat.unifiedControls.title': 'コントロール',
   'chat.unifiedControls.model.title': 'モデル',
   'chat.unifiedControls.model.noRecent': '最近のモデルはありません',

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

@@ -1862,6 +1862,12 @@ export const dict: Record<I18nKey, string> = {
   'chat.container.returnToParent.title': '상위 세션으로 돌아가기',
   'chat.container.returnToParent.label': '상위',
   'chat.container.readOnlySubagentPromptBanner': '하위 에이전트 세션에는 프롬프트를 보낼 수 없습니다.',
+  'chat.container.sessionLoadError.title': '세션을 불러올 수 없습니다',
+  'chat.container.sessionLoadError.description': '연결을 확인한 후 이 세션을 다시 불러오세요.',
+  'chat.container.sessionLoadError.retry': '다시 시도',
+  'sessions.sidebar.group.empty.loadingSessions': '세션을 불러오는 중…',
+  'sessions.sidebar.group.empty.loadFailed': '세션을 새로 고칠 수 없습니다.',
+  'sessions.sidebar.group.empty.retry': '다시 시도',
   'chat.unifiedControls.title': '컨트롤',
   'chat.unifiedControls.model.title': '모델',
   'chat.unifiedControls.model.noRecent': '최근 모델 없음',

packages/ui/src/lib/i18n/messages/pl.ts

@@ -749,6 +749,12 @@ export const dict: Record<I18nKey, string> = {
   'chat.container.returnToParent.title': 'Powrót do sesji nadrzędnej',
   'chat.container.returnToParent.label': 'Nadrzędna',
   'chat.container.readOnlySubagentPromptBanner': 'Sesje podagentów nie mogą otrzymywać promptów.',
+  'chat.container.sessionLoadError.title': 'Nie udało się wczytać sesji',
+  'chat.container.sessionLoadError.description': 'Sprawdź połączenie i spróbuj ponownie wczytać tę sesję.',
+  'chat.container.sessionLoadError.retry': 'Spróbuj ponownie',
+  'sessions.sidebar.group.empty.loadingSessions': 'Wczytywanie sesji…',
+  'sessions.sidebar.group.empty.loadFailed': 'Nie udało się odświeżyć sesji.',
+  'sessions.sidebar.group.empty.retry': 'Spróbuj ponownie',
   'chat.unifiedControls.title': 'Kontrolki',
   'chat.unifiedControls.model.title': 'Model',
   'chat.unifiedControls.model.noRecent': 'Brak ostatnich modeli',

packages/ui/src/lib/i18n/messages/pt-BR.ts

@@ -1838,6 +1838,12 @@ export const dict: Record<I18nKey, string> = {
   "chat.container.returnToParent.title": "Voltar para a sessão principal",
   "chat.container.returnToParent.label": "Principal",
   "chat.container.readOnlySubagentPromptBanner": "Sessões de subagente não podem receber prompts.",
+  "chat.container.sessionLoadError.title": "Não foi possível carregar a sessão",
+  "chat.container.sessionLoadError.description": "Verifique a conexão e tente carregar esta sessão novamente.",
+  "chat.container.sessionLoadError.retry": "Tentar novamente",
+  "sessions.sidebar.group.empty.loadingSessions": "Carregando sessões…",
+  "sessions.sidebar.group.empty.loadFailed": "Não foi possível atualizar as sessões.",
+  "sessions.sidebar.group.empty.retry": "Tentar novamente",
   "chat.unifiedControls.title": "Controles",
   "chat.unifiedControls.model.title": "Modelo",
   "chat.unifiedControls.model.noRecent": "Não há modelos recentes",

packages/ui/src/lib/i18n/messages/uk.ts

@@ -1838,6 +1838,12 @@ export const dict: Record<I18nKey, string> = {
   "chat.container.returnToParent.title": "Повернутися до батьківської сесії",
   "chat.container.returnToParent.label": "Батьківська",
   "chat.container.readOnlySubagentPromptBanner": "Сесії субагентів не можна запитувати.",
+  "chat.container.sessionLoadError.title": "Не вдалося завантажити сесію",
+  "chat.container.sessionLoadError.description": "Перевірте з’єднання та спробуйте завантажити цю сесію ще раз.",
+  "chat.container.sessionLoadError.retry": "Спробувати знову",
+  "sessions.sidebar.group.empty.loadingSessions": "Завантаження сесій…",
+  "sessions.sidebar.group.empty.loadFailed": "Не вдалося оновити сесії.",
+  "sessions.sidebar.group.empty.retry": "Спробувати знову",
   "chat.unifiedControls.title": "Елементи керування",
   "chat.unifiedControls.model.title": "Модель",
   "chat.unifiedControls.model.noRecent": "Немає останніх моделей",

packages/ui/src/lib/i18n/messages/zh-CN.ts

@@ -1826,6 +1826,12 @@ export const dict: Record<I18nKey, string> = {
   'chat.container.returnToParent.title': '返回父会话',
   'chat.container.returnToParent.label': '父级',
   'chat.container.readOnlySubagentPromptBanner': '无法向子智能体会话发送提示。',
+  'chat.container.sessionLoadError.title': '无法加载会话',
+  'chat.container.sessionLoadError.description': '请检查连接，然后重新加载此会话。',
+  'chat.container.sessionLoadError.retry': '重试',
+  'sessions.sidebar.group.empty.loadingSessions': '正在加载会话…',
+  'sessions.sidebar.group.empty.loadFailed': '无法刷新会话。',
+  'sessions.sidebar.group.empty.retry': '重试',
   'chat.unifiedControls.title': '控制',
   'chat.unifiedControls.model.title': '模型',
   'chat.unifiedControls.model.noRecent': '没有最近使用的模型',

packages/ui/src/lib/i18n/messages/zh-TW.ts

@@ -1830,6 +1830,12 @@ export const dict: Record<I18nKey, string> = {
   'chat.container.returnToParent.title': '返回父會話',
   'chat.container.returnToParent.label': '父級',
   'chat.container.readOnlySubagentPromptBanner': '無法向子 Agent 會話傳送提示。',
+  'chat.container.sessionLoadError.title': '無法載入工作階段',
+  'chat.container.sessionLoadError.description': '請檢查連線，然後重新載入此工作階段。',
+  'chat.container.sessionLoadError.retry': '再試一次',
+  'sessions.sidebar.group.empty.loadingSessions': '正在載入工作階段…',
+  'sessions.sidebar.group.empty.loadFailed': '無法重新整理工作階段。',
+  'sessions.sidebar.group.empty.retry': '再試一次',
   'chat.unifiedControls.title': '控制',
   'chat.unifiedControls.model.title': '模型',
   'chat.unifiedControls.model.noRecent': '沒有最近使用的模型',