Play Framework

refactor(ws): migrate WSAsync from JDK HttpClient to OkHttp 5 (PF-104)

The framework's outbound WS API now sits on OkHttp 5.3.2 instead of
java.net.http.HttpClient. Two reasons drove this:

1. h2c upgrade hang. The JDK client sends `Upgrade: h2c` on cleartext HTTP
   to advertise HTTP/2 willingness. Servers that echo the header without
   actually delivering the upgrade preface (notably LM Studio's Express
   front-end) wedge the JDK client until the request timeout fires. OkHttp
   does not send the upgrade on cleartext, so this failure mode is
   structurally absent.

2. Virtual-thread cleanliness. Okio 3's read path has no synchronized
   blocks, so an OkHttpClient.Dispatcher backed by
   Executors.newVirtualThreadPerTaskExecutor() lets blocking socket reads
   unmount during the read. The JDK client only got the same property via
   AsynchronousSocketChannel.

The public WS surface (`WS.url(...).get()`, `WSRequest`, `HttpResponse`)
is unchanged. Internals:

- Two shared OkHttpClient instances (follow-redirects on/off) over one
  ConnectionPool (32 idle / 5min keep-alive) and one Dispatcher (VT executor).
- Per-call timeout is applied via newBuilder().callTimeout(...) so the
  shared client stays unmodified.
- Proxy auth migrated to okhttp3.Authenticator (Proxy-Authorization on 407).
- ssl.keyStore / ssl.cavalidation=false still respected via OkHttp's
  sslSocketFactory() + hostnameVerifier().
- BodyPublishers -> RequestBody; InputStream bodies wrapped in a one-shot
  RequestBody backed by okio.Source.
- HttpJdkResponse renamed to HttpAsyncResponse (no external callers).
- Response body is read eagerly into a byte[] inside the constructor with
  try-with-resources on the Response, matching the prior eager-bytes
  semantics and avoiding leaked connections.

Dependency changes (transitiveDependencies: false means everything is
declared explicitly):

- com.squareup.okhttp3:okhttp:5.3.2 (alias pom, 767-byte jar)
- com.squareup.okhttp3:okhttp-jvm:5.3.2 (actual bytecode)
- com.squareup.okhttp3:okhttp-sse:5.3.2
- com.squareup.okio:okio:3.16.4 (alias)
- com.squareup.okio:okio-jvm:3.16.4 (actual bytecode)
- org.jetbrains.kotlin:kotlin-stdlib:2.2.21

Documentation: libs.textile claimed WS used the long-removed Async HTTP
Client. Updated to reflect OkHttp 5 + virtual-thread dispatcher.

Verified: `ant test` (clean + jar + unittest + integration-test) green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>