HS E36: socket URL parsing + hs-socket-register! runtime (+3 tests)

- parser.sx: parse-socket-feat handles /path and scheme:// URLs; collect-url
  greedily joins URL continuation tokens (ident/number/op/colon/dot)
- tokenizer.sx: fix :// not treated as line comment (lookback check)
- compiler.sx: emit-socket compiles socket AST to hs-socket-register! call
- runtime.sx: hs-socket-register! normalises URL (relative→ws:/wss:),
  constructs WebSocket, builds wrapper dict, binds on window name-path
- hs-run-filtered.js: WebSocket mock uses plain object (not JS array) so
  host-global returns a foreign value rather than SX list; host-get idx works

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/hyperscript/compiler.sx

@@ -787,6 +787,31 @@
               (quote fn)
               (cons (quote me) (map make-symbol params))
               (cons (quote do) (map hs-to-sx body)))))))
+    (define
+      emit-socket
+      (fn
+        (ast)
+        (let
+          ((name-path (nth ast 1))
+           (url (nth ast 2))
+           (timeout-ms (nth ast 3))
+           (on-msg (nth ast 4)))
+         (let
+           ((handler
+             (if
+               (nil? on-msg)
+               nil
+               (let
+                 ((body (hs-to-sx (nth on-msg 2))))
+                 (list (quote fn) (list (quote event)) body))))
+             (json?-val (if (nil? on-msg) false (nth on-msg 1))))
+           (list
+             (quote hs-socket-register!)
+             (cons (quote list) name-path)
+             url
+             (if (nil? timeout-ms) nil (hs-to-sx timeout-ms))
+             handler
+             json?-val)))))
     (fn
       (ast)
       (cond
@@ -2075,6 +2100,7 @@
                           (quote _hs-def-val))
                         (quote _hs-def-val))))))
               ((= head (quote behavior)) (emit-behavior ast))
+              ((= head (quote socket)) (emit-socket ast))
               ((= head (quote sx-eval))
                 (let
                   ((src (nth ast 1)))