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/sync/session-prefetch-cache.test.ts

@@ -0,0 +1,50 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import {
+  clearDirectorySessionPrefetch,
+  clearRuntimeSessionPrefetch,
+  getSessionPrefetch,
+  setSessionPrefetch,
+} from "./session-prefetch-cache"
+
+const runtimes = ["prefetch-runtime-a", "prefetch-runtime-b"]
+
+afterEach(() => {
+  for (const runtimeKey of runtimes) clearRuntimeSessionPrefetch(runtimeKey)
+})
+
+describe("session prefetch cache", () => {
+  test("isolates colliding directory and session IDs by runtime", () => {
+    setSessionPrefetch({ directory: "/repo", sessionID: "session", limit: 10, complete: false, runtimeKey: runtimes[0] })
+    setSessionPrefetch({ directory: "/repo", sessionID: "session", limit: 20, complete: true, runtimeKey: runtimes[1] })
+
+    expect(getSessionPrefetch("/repo", "session", runtimes[0])?.limit).toBe(10)
+    expect(getSessionPrefetch("/repo", "session", runtimes[1])?.limit).toBe(20)
+  })
+
+  test("clears only the owning runtime and directory", () => {
+    setSessionPrefetch({ directory: "/repo-a", sessionID: "session", limit: 10, complete: false, runtimeKey: runtimes[0] })
+    setSessionPrefetch({ directory: "/repo-b", sessionID: "session", limit: 20, complete: false, runtimeKey: runtimes[0] })
+    setSessionPrefetch({ directory: "/repo-a", sessionID: "session", limit: 30, complete: false, runtimeKey: runtimes[1] })
+
+    clearDirectorySessionPrefetch("/repo-a", runtimes[0])
+
+    expect(getSessionPrefetch("/repo-a", "session", runtimes[0])).toBe(undefined)
+    expect(getSessionPrefetch("/repo-b", "session", runtimes[0])?.limit).toBe(20)
+    expect(getSessionPrefetch("/repo-a", "session", runtimes[1])?.limit).toBe(30)
+  })
+
+  test("bounds retained metadata globally", () => {
+    for (let index = 0; index <= 200; index += 1) {
+      setSessionPrefetch({
+        directory: "/repo",
+        sessionID: `session-${index}`,
+        limit: index,
+        complete: false,
+        runtimeKey: runtimes[0],
+      })
+    }
+
+    expect(getSessionPrefetch("/repo", "session-0", runtimes[0])).toBe(undefined)
+    expect(getSessionPrefetch("/repo", "session-200", runtimes[0])?.limit).toBe(200)
+  })
+})