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/runtime.sx

@@ -2525,3 +2525,56 @@
   (fn
     (fn-name args)
     (let ((fn (host-global fn-name))) (if fn (host-call-fn fn args) nil))))
+
+;; ── WebSocket / socket feature ───────────────────────────────────
+
+(define
+  hs-socket-register!
+  (fn
+    (name-path url timeout-ms handler json?)
+    ;; 1. Normalise URL — absolute ws/wss pass through; relative paths get scheme+host
+    (let
+      ((ws-url
+        (cond
+          ((or (starts-with? url "ws://") (starts-with? url "wss://")) url)
+          (true
+            (let
+              ((proto (host-get (host-global "location") "protocol"))
+                (h (host-get (host-global "location") "host")))
+              (str (if (= proto "https:") "wss:" "ws:") "//" h url))))))
+      ;; 2. Construct WebSocket
+      (let
+        ((ws (host-new "WebSocket" ws-url)))
+        ;; 3. Build wrapper dict
+        (let
+          ((wrapper
+            {:raw ws
+             :url ws-url
+             :timeout timeout-ms
+             :pending {}
+             :handler handler
+             :json? json?
+             :closed? false}))
+          ;; 4. Wire RPC proxy via JS factory (if available)
+          (let
+            ((proxy-factory (host-global "_hs_make_rpc_proxy")))
+            (when proxy-factory
+              (host-set! wrapper "rpc"
+                (host-call proxy-factory "call" nil wrapper))))
+          ;; 5. Bind wrapper on window, walking name-path
+          (define
+            bind-path!
+            (fn
+              (obj path)
+              (if
+                (= (len path) 1)
+                (host-set! obj (first path) wrapper)
+                (let
+                  ((key (first path))
+                    (rest-path (rest path)))
+                  (let
+                    ((next (or (host-get obj key) {})))
+                    (host-set! obj key next)
+                    (bind-path! next rest-path))))))
+          (bind-path! (host-global "window") name-path)
+          wrapper)))))