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

.agents/skills/openchamber-change-discipline/SKILL.md

@@ -82,7 +82,7 @@ Use `package.json` scripts as the command source of truth.
 | Executable source | Focused tests plus package-scoped type-check and lint |
 | Cross-workspace/shared contract | Workspace-wide type-check and lint plus affected builds/tests |
 | Added/deleted/renamed source file, export/type/entrypoint/import shape | `bun run dead-code` in addition to relevant checks |
-| Persisted or external contract | Compatibility and round-trip tests; conversion/malformed-old-data tests when old data needs migration; failed-write/migration rollback tests |
+| Persisted or external contract | Compatibility and round-trip tests plus the applicable failure/ordering cases: missing-versus-empty, malformed data, stale reads versus newer mutations, out-of-order writes, lifecycle handling for debounced writes, conversion, and failed-write/migration rollback |
 | Dependency or lockfile | Workspace-wide checks and affected builds |
 | Generated asset | Regeneration check plus consumer build/test |
 | Docs-only or isolated config | Narrow syntax/schema/link validation; do not run unrelated full suites |