Add HyperSX view tab: indentation-based alternative syntax for SX

sx->hypersx transform converts parsed SX to a readable indentation-based
format: CSS selector shorthand (div.card#main), signal sugar (@count,
signal(), :=, <-), string interpolation ("Count: {@count}"), and
structural keywords (when, if, let, map, for).

Implemented as pure SX in web/lib/hypersx.sx, loaded in browser via
js_of_ocaml platform. Added as "hypersx" tab in the tree editor.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/browser/sx-platform.js

@@ -253,6 +253,7 @@
       "sx/adapter-dom.sx",
       // Boot helpers (platform functions in pure SX)
       "sx/boot-helpers.sx",
+      "sx/hypersx.sx",
       // Web framework
       "sx/engine.sx",
       "sx/orchestration.sx",