Add TCO for parser loops in JS bootstrapper, enable SX_USE_REF

The JS parser transpiled from parser.sx used tail-recursive functions
(readStrLoop, skipWs, readListLoop, etc.) which overflow the stack on
large inputs — the bootstrapper page highlights 100KB of Python and
143KB of JavaScript, producing 7620 spans in a 907KB response.

The bootstrapper now detects zero-arg self-tail-recursive functions and
emits them as while(true) loops with continue instead of recursive
calls. Tested with 150K char strings and 8000 sibling elements.

Also enables SX_USE_REF=1 in dev via x-dev-env anchor.

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

docker-compose.dev.yml

@@ -10,6 +10,7 @@
 x-dev-env: &dev-env
   RELOAD: "true"
   WORKERS: "1"
+  SX_USE_REF: "1"
 
 x-sibling-models: &sibling-models
   # Every app needs all sibling __init__.py + models/ for cross-domain SQLAlchemy imports