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/components/views/DiffView.tsx

@@ -3,6 +3,7 @@ import React from 'react';
 import { useUIStore } from '@/stores/useUIStore';
 import { useEffectiveDirectory } from '@/hooks/useEffectiveDirectory';
 import { useGitStore, useGitStatus, useIsGitRepo, useGitLoadingStatus } from '@/stores/useGitStore';
+import { getRuntimeKey } from '@/lib/runtime-switch';
 import { cn } from '@/lib/utils';
 import type { GitStatus } from '@/lib/api/types';
 import {
@@ -667,6 +668,7 @@ const MultiFileDiffEntry = React.memo<MultiFileDiffEntryProps>(({
         setIsLoading(true);
 
         let cancelled = false;
+        const runtimeKey = getRuntimeKey();
         const contextLines = loadFullFiles ? FULL_CONTEXT_DIFF_LINES : DEFAULT_CONTEXT_DIFF_LINES;
         const fetchPromise = isImageFile(file.path)
             ? git.getGitFileDiff(directory, { path: file.path, staged })
@@ -697,7 +699,7 @@ const MultiFileDiffEntry = React.memo<MultiFileDiffEntryProps>(({
                     if (staged) {
                         setStagedDiffData(nextDiff);
                     } else {
-                        setDiff(directory, file.path, nextDiff);
+                        setDiff(directory, file.path, nextDiff, runtimeKey);
                     }
                 }
                 setIsLoading(false);
@@ -1494,6 +1496,7 @@ export const DiffView: React.FC<DiffViewProps> = ({
         }
 
         setOpeningEditorFilePath(filePath);
+        const runtimeKey = getRuntimeKey();
         try {
             let targetLine: number | null = null;
 
@@ -1525,7 +1528,7 @@ export const DiffView: React.FC<DiffViewProps> = ({
                     isBinary: response.isBinary,
                 };
                 if (!activeDiffStaged) {
-                    setDiff(effectiveDirectory, filePath, diffForNavigation);
+                    setDiff(effectiveDirectory, filePath, diffForNavigation, runtimeKey);
                 }
             }