Add scoped postbox template previews

README.md

@@ -48,6 +48,12 @@ Unit-specific addresses are resolved lazily and remain stable through vacancy
 and reassignment. Exact postboxes remain available for exceptional
 responsibilities or case/service contexts.
 
+Subtree templates select an explicit Organizations structure and optional
+hierarchical relation types. The administration UI can dry-run a draft against
+the current organization and incumbency state, showing generated addresses,
+vacancy, existing targets, collisions, and hierarchy diagnostics without
+materializing data.
+
 Users holding several functions may group selected postboxes into unified
 inbox views. These are query projections only: messages, address, read state,
 retention, and evidence remain attached to their source postboxes.
@@ -84,7 +90,8 @@ addresses, exact function-bound Postboxes, current IDM assignment access
 decisions, vacancy status, idempotent producer delivery, source-preserving
 message and attachment references, personal read/acknowledgement receipts,
 unified inbox projections, access evidence, an inbox route, and tenant
-administration. Published template revisions can also opt into bounded linked
+administration. Grouping summaries expose batched total and unread counts for
+currently visible sources. Published template revisions can also opt into bounded linked
 copies through one explicit organization structure. Classification, producer,
 retention, stop, depth, target-template, and target-function gates are frozen
 at delivery time and exposed through delivery evidence and the routing dry-run