perf: reduce re-renders, fix mobile keyboard handling, add chunk load recovery, and improve PATH management (#1028)

* fix: exclude file content from reverted prompt text

Revert and fork now restore only the user's original prompt, not server-injected file content
Uses existing isSyntheticPart helper for type-safe filtering

* fix: keep scrollbar visible when hovering over thumb

* fix: prevent ESC abort from triggering when terminal is focused

* fix: pass directory to permission/question reply calls so approvals actually resolve

* fix: default model selection not responding after Base UI migration

* fix: prevent modal content from shifting and clipping footer buttons

* fix: improve session switching performance and add sub-agent export with prompt collapse

Defer viewport anchor saving to eliminate ~800ms UI freeze when switching sessions
Add export dialog to include sub-agent tasks recursively in markdown export
Add collapse chevron button for expanded user prompts in sticky header

* fix: resolve sidebar scroll and TDZ crash in session sidebar

* perf: reduce CPU overhead and re-renders across chat, layout, and settings

* fix: position collapse button at top of message and prevent ESC abort in terminal

* fix: position collapse button at top and add padding only when expanded

* refactor: extract shared PATH utilities and mobile keyboard hook

* refactor: import shared path-utils in electron, use module-level style constants

- Electron now imports pathLooksUserConfigured/mergePathValues from
  shared path-utils.js instead of inline duplication
- ToolPart collapsedCustomStyle moved from useMemo([]) to module const

* fix: resolve remaining merge conflicts and type errors

- Remove duplicate variable declarations in SessionNodeItem
- Remove orphaned export callback body from conflict resolution
- Fix HelpDialog description -> descriptionKey (i18n rename)

* fix: resolve type-check and lint errors in session-actions.test.ts

- Added missing bun:test type declarations (beforeEach, mock, mock.module)
- Removed unused State import
- Replaced 'as any' casts with proper OpencodeClient and ChildStoreManager types
- Added eslint-disable for unused _ parameter in mock function

* fix PR 1028 export and PATH edge cases

* fix startup retry exhaustion state

* remove opencode package lock change

* fix sub-session rename cancellation

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/sync/session-ui-store.ts

@@ -358,6 +358,10 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
     }
 
     const previousSessionId = get().currentSessionId
+
+    // Set currentSessionId immediately so the skeleton renders without delay.
+    set({ currentSessionId: id })
+
     const directoryState = useDirectoryStore.getState()
 
     const sessionDir = resolveSessionDirectory(
@@ -376,20 +380,21 @@ export const useSessionUIStore = create<SessionUIState>()((set, get) => ({
       console.warn("Failed to set OpenCode directory for session switch:", e)
     }
 
-    // Save viewport anchor for previous session
+    // Defer viewport anchor save for previous session — not needed for the
+    // skeleton to render and reads messages which can be expensive.
     if (previousSessionId && previousSessionId !== id) {
-      const memState = useViewportStore.getState().sessionMemoryState.get(previousSessionId)
-      if (!memState?.isStreaming) {
-        const prevMessages = getSyncMessages(previousSessionId)
-        if (prevMessages.length > 0) {
-          useViewportStore.getState().updateViewportAnchor(previousSessionId, prevMessages.length - 1)
+      const prevId = previousSessionId
+      setTimeout(() => {
+        const memState = useViewportStore.getState().sessionMemoryState.get(prevId)
+        if (!memState?.isStreaming) {
+          const prevMessages = getSyncMessages(prevId)
+          if (prevMessages.length > 0) {
+            useViewportStore.getState().updateViewportAnchor(prevId, prevMessages.length - 1)
+          }
         }
-      }
+      }, 0)
     }
 
-    set({ currentSessionId: id })
-
-    // Mark session viewed in notification store + update active session ref
     // Mark session viewed in notification store + update active session ref
     if (id) {
       markSessionViewed(id)