docs: Fix README inaccuracies on parser selection and form value types

- Selection is by the full media type (type/subtype), not the RFC
  9110 subtype. Note that lookup is case-insensitive.
- After coercion, form list values are not strictly List<String> —
  an integer-array property yields List<Long>, etc. Describe the
  pre- and post-coercion shape correctly.

Author: thced

README.md

@@ -102,12 +102,12 @@ The rest is identical.
 
 ### Request body content types
 
-The server reads `requestBody.content` from the spec and selects a parser by `Content-Type` subtype:
+The server reads `requestBody.content` from the spec and selects a parser by the request's media type (the bare `type/subtype` from `Content-Type`, e.g. `application/json`; lookup is case-insensitive):
 
 | Content type                          | Parser                                                                       | Coercion |
 | ------------------------------------- | ---------------------------------------------------------------------------- | -------- |
 | `application/json`                    | Caller-supplied `JsonMapper`                                                 | No — strict against the schema |
-| `application/x-www-form-urlencoded`   | Built-in. `Map<String, Object>` (string or `List<String>` for repeated keys) | Yes — field values coerced to the property schema type (integer / number / boolean / array of those) |
+| `application/x-www-form-urlencoded`   | Built-in. `Map<String, Object>`. A single value is a `String`; repeated keys produce a `List`. After coercion the element type tracks the schema (e.g. an `integer` array yields `List<Long>`). | Yes — field values coerced to the property schema type (integer / number / boolean / array of those) |
 | `text/plain`                          | Built-in. Decoded `String`                                                   | No — schema should be `type: string` |
 
 Form-field coercion mirrors the rules already used at the parameter boundary: the wire is string-only by definition, so a property typed as `integer` accepts `"42"` and yields `42`. Coercion failures surface as RFC-7807 `400` responses with a JSON-pointer to the failing field.