docs: add a Role in the framework section to every module README

Each module README now says where the module sits in the dependency
graph, why it is its own module, and lists use cases for application
developers.

modules/wire/README.md

@@ -10,6 +10,16 @@ JSON response helpers and value types that keep API bodies byte-compatible with
 
 `wire` is the lowest layer of the HTTP stack: it decides how a Go value becomes response bytes. Its helpers reproduce what `json_encode` and Carbon produce in a WinterCMS or Laravel app (unescaped HTML characters, no trailing newline, `+00:00` timestamps, nullable booleans, `[]` rather than `null` for empty lists), so an endpoint ported from PHP returns the same body its existing clients already parse. [surf](../surf/README.md) uses it for the opaque 500 response of its panic recovery, and application handlers use it directly for their JSON responses.
 
+## Role in the framework
+
+A dependency-free leaf for response shapes. `surf` and `lighthouse` use it, and so do plugin controllers. It is separate so every handler produces the same JSON as the PHP backend being replaced, byte for byte.
+
+Use cases:
+
+- Return paginated lists and error envelopes in the shape an existing frontend expects.
+- Encode timestamps, nullable booleans and empty lists the way Laravel serializes them.
+- Port endpoints one at a time without the frontend noticing the backend changed.
+
 ## Features
 
 - `wire.WriteJSON` encodes a value with HTML escaping disabled and without the trailing newline `encoding/json` adds, then sets `Content-Type: application/json` and the status code. If encoding fails, it writes the opaque 500 body instead of a partial response.