fix(settings): close cross-namespace, dispatch, and lifecycle races from second review

Confirmed and fixed, each with a regression test that failed first:

- Concurrent writes to different namespaces lost whole sections on disk
  (each persist rendered the full document from a stale text): the local
  provider serializes render->write->rename->text-commit on one internal
  persist chain shared by every namespace queue.
- One throwing settings/updated listener starved the rest (cordis emit
  stops at the first throw): commit fans out per listener via
  events.dispatch, contains individual failures, and rethrows the first
  INVARIANT-coded error only after every listener ran.
- Write queues ignored fiber/service lifecycle: the base init now
  registers a teardown that refuses new writes and drains queued chains;
  queued tasks re-verify service liveness and namespace ownership before
  running and again before committing, so a registrant disposed
  mid-flight is never notified and a disposed service never commits.
- Async watcher invocations could interleave (a slow stale call applied
  last): each watcher carries a serialized invocation chain — one call
  at a time, in commit order; JSDoc/doc pages state the async timing.
- update/replace borrowed the caller's object until the queued task ran:
  inputs are structured-clone snapshotted at call time; non-cloneable
  plain objects reject with a typed error.
- Composition guard now proves the documented fallback: the consumer
  uses the optional scoped-inject shape and boots both with the settings
  entry (hot publish) and without it (entry-config resolution, no scope).
- core-data-structures index: settings.md row added to the sub-page
  table in core.md/core.zh.md.

Both packages hold per-file 100% coverage across repeated runs.

docs/core-data-structures/settings.zh.md

@@ -46,8 +46,9 @@ interface SettingsScope<T> {
   /** Current resolved value: schema defaults, then `base`, then the user layer. */
   get(): T
   /**
-   * Observe committed changes to this namespace's resolved value. A callback
-   * may be async; a rejection is contained and logged like a sync throw.
+   * Observe committed changes to this namespace's resolved value. Invocations
+   * of one callback run asynchronously, one at a time, in commit order; a
+   * rejection is contained and logged like a sync throw.
    * @param callback - invoked after each commit with the next and previous values.
    * @returns the disposer removing this observer.
    */