fix: address review round two

- listChildren contains per-child projection faults on both ladder rungs
  (any registered unit's fold/schema rejection maps to that child's corrupt
  diagnostic) and pins the whole-enumeration listing-failure rethrow
- the base bundle mounts session-projection (web-app's own insert retired
  to avoid the double mount); stale composition comment updated
- the shared projections-unavailable wire face is pinned across
  list/history/prompt; retired session-query arms removed from the catalog
  paths
- the design note records the unknown-parent semantics shift and the
  fold-fault isolation rule

pnpm-lock.yaml

@@ -946,6 +946,9 @@ importers:
       '@deepseek-ai/dsh-session-persistence-jsonl':
         specifier: workspace:^
         version: link:../../session-persistence/session-persistence-jsonl
+      '@deepseek-ai/dsh-session-projection':
+        specifier: workspace:^
+        version: link:../../session-projection/session-projection
       '@deepseek-ai/dsh-session-query-sqlite':
         specifier: workspace:^
         version: link:../../session-query/session-query-sqlite
@@ -1191,9 +1194,6 @@ importers:
       '@deepseek-ai/dsh-host-webserver':
         specifier: workspace:^
         version: link:../../host/webserver
-      '@deepseek-ai/dsh-session-projection':
-        specifier: workspace:^
-        version: link:../../session-projection/session-projection
       '@deepseek-ai/dsh-session-projection-cache':
         specifier: workspace:^
         version: link:../../session-projection/session-projection-cache