fix(settings): harden seam and provider per review findings

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

- Concurrent update() lost patches (merge over one stale snapshot):
  per-namespace serialized write queues; a failed write cannot poison
  the queue for later writers.
- Fixed-name .tmp write followed planted symlinks and kept stale modes:
  random-suffix sibling, exclusive-create (wx), 0600, cleanup on
  failure, then rename.
- A throwing settings/updated listener escaped commit and permanently
  wedged the provider reload chain (rejected refreshTask): commit now
  contains listener failures (INVARIANT-coded errors still propagate),
  async watcher rejections are adopted and contained
  (watch callbacks are officially void | Promise<void>), and the
  provider chains refreshes on a settled tail with an error log.
- No way to remove a user override: scope/service replace(section)
  sets the user section wholesale; replace({}) re-inherits base and
  schema defaults.
- The three-primitive provider contract did not hold (base never
  called load()): the base Service.init loads and publishes once;
  settings-local delegates via yield* super[Service.init]().
- Dispose did not quiesce: teardown flags closed, closes the watcher,
  then awaits queued/in-flight reloads; closed is re-checked across
  await points.
- Invariant now checks the authoritative relation with the seam's own
  deepEqualJson: emitted next must equal settings.get(ns), and
  next/prev must differ structurally (cosmokit dependency dropped).
- New docs/core-data-structures/settings.{md,zh.md} with type-equiv
  blocks + manifest entries; catalog types moved from exemptions to
  LINK_MAP; website page registered.

Both packages stay at per-file 100% coverage.

packages/settings/settings-local/README.md

@@ -18,7 +18,8 @@ Defaulting is one explicit `resolveSpec(config)` step; an unsupported extension
 ## Behavior
 
 - **Boot fails loud, reload keeps last-good.** An existing-but-invalid document fails plugin load; once live, an unreadable or unparsable edit warns and keeps the last good sections. A missing document resolves every namespace from defaults and `base`; deleting it publishes the same empty state.
-- **Write-back is atomic and owner-only.** `persist` writes `<path>.tmp` with mode `0600` and renames over the target. YAML writes patch one namespace in the comment-preserving document; JSON re-serializes.
+- **Write-back is atomic, owner-only, and symlink-proof.** `persist` exclusive-creates a random-suffix temp sibling with mode `0600` (`wx` refuses to follow a planted symlink) and renames over the target, cleaning the temp up on failure. YAML writes patch one namespace in the comment-preserving document; JSON re-serializes.
+- **Dispose quiesces.** Teardown stops accepting watcher events, closes the watcher, then waits out any queued or in-flight reload, so nothing publishes after disposal.
 - **Self-write suppression by content.** The provider caches the last good text; a watcher event whose content equals the cache (its own write included) is a no-op.
 
 ## Model Experience