dream: websockets — upgrade + send/receive/close/broadcast + 16 tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/dream-on-sx.md

@@ -69,7 +69,7 @@ The five types: `request`, `response`, `handler = request -> response`, `middlew
       - [x] `dream-multipart req` — multipart form data (in-memory, not yet streaming).
       - [x] CSRF middleware: stateless signed tokens, session-scoped.
       - [x] `dream-csrf-tag req` — returns hidden input fragment for SX templates.
-- [ ] **WebSockets** in `lib/dream/websocket.sx`:
+- [x] **WebSockets** in `lib/dream/websocket.sx`:
       - `dream-websocket handler` — upgrades request; handler `(fn (ws) ...)`.
       - `dream-send ws msg`, `dream-receive ws`, `dream-close ws`.
 - [ ] **Static files:** `dream-static root-path` — serves files, ETags, range requests.
@@ -174,6 +174,14 @@ Confirm scope before starting; some of these may be addable as Dream-internal he
   in file content preserved). `dream-multipart-field` / `dream-multipart-file`
   accessors. In-memory, not streaming (noted for future). `\r`/`\n` string escapes
   work in SX literals.
+- **2026-06-07 — WebSockets** (`lib/dream/websocket.sx`, 16 tests). `dream-websocket
+  handler` wraps a `(fn (ws) …)` into an ordinary handler returning a 101 upgrade
+  response carrying the ws handler (`dream-websocket?` / `dream-ws-handler` for the
+  host to detect + dispatch). `dream-send` / `dream-receive` / `dream-close` /
+  `dream-ws-open?` / `dream-ws-broadcast` operate over an injectable io; production io
+  is `(perform op)`, tests use `dream-mock-ws` (in-memory inbox/outbox/closed via the
+  cell pattern) with `dream-ws-sent` / `dream-ws-closed?` introspection and
+  `dream-ws-run` to drive a handler. Echo loop + room broadcast verified.
 
 ## Blockers