feat: implement permission-aware search baseline

README.md

@@ -3,3 +3,16 @@
 <!-- govoplan-repository-type:start -->
 **Repository type:** module (platform).
 <!-- govoplan-repository-type:end -->
+
+Permission-aware global and contextual search for GovOPlaN.
+
+The module works with its built-in database index and no external search
+service. PostgreSQL uses native full-text search; SQLite provides a bounded
+development fallback. Other modules may:
+
+- register a live search provider in their module manifest
+- write authorized documents through the `search.index_writer` capability
+- announce context-sensitive WebUI search scopes through `search.contexts`
+
+An optional OpenSearch adapter is a later provider, not a hard dependency.
+Source modules remain responsible for defining visibility and authorization.