Phase 5 cleanup: remove legacy HTML components, fix nav-tree fragment

- Remove old raw! layout components (~app-head, ~app-layout, ~oob-response,
  ~header-row, ~menu-row, ~oob-header, ~header-child) from layout.sexp
- Convert nav-tree fragment from Jinja HTML to sexp source, fixing the
  "Unexpected character: ." parse error caused by HTML leaking into sexp
- Add _as_sexp() helper to safely coerce HTML fragments to ~rich-text
- Fix federation/sexp/search.sexpr extra closing paren
- Remove dead _html() wrappers from blog and account sexp_components
- Remove stale render import from cart sexp_components
- Add dev_watcher.py to auto-reload on .sexp/.sexpr/.js/.css changes
- Add test_parse_all.py to parse-check all 59 sexpr/sexp files
- Fix test assertions for sx- attribute prefix (was hx-)
- Add sexp.js version logging for cache debugging

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

shared/static/scripts/sexp.js

@@ -159,7 +159,8 @@
       return new Symbol(name);
     }
 
-    throw parseErr("Unexpected character: " + ch, this);
+    var ctx = this.text.substring(Math.max(0, this.pos - 40), this.pos + 40);
+    throw parseErr("Unexpected character: " + ch + " | context: «" + ctx.replace(/\n/g, "\\n") + "»", this);
   };
 
   function isDigit(c) { return c >= "0" && c <= "9"; }
@@ -1949,8 +1950,11 @@
   // Auto-init in browser
   // =========================================================================
 
+  Sexp.VERSION = "2026-03-01a";
+
   if (typeof document !== "undefined") {
     var init = function () {
+      console.log("[sexp.js] v" + Sexp.VERSION + " init");
       Sexp.processScripts();
       Sexp.hydrate();
       SxEngine.process();