Phase 3: Client-side routing with SX page registry + routing analyzer demo

Add client-side route matching so pure pages (no IO deps) can render
instantly without a server roundtrip. Page metadata serialized as SX
dict literals (not JSON) in <script type="text/sx-pages"> blocks.

- New router.sx spec: route pattern parsing and matching (6 pure functions)
- boot.sx: process page registry using SX parser at startup
- orchestration.sx: intercept boost links for client routing with
  try-first/fallback — client attempts local eval, falls back to server
- helpers.py: _build_pages_sx() serializes defpage metadata as SX
- Routing analyzer demo page showing per-page client/server classification
- 32 tests for Phase 2 IO detection (scan_io_refs, transitive_io_refs,
  compute_all_io_refs, component_pure?) + fallback/ref parity
- 37 tests for Phase 3 router functions + page registry serialization
- Fix bootstrap_py.py _emit_let cell variable initialization bug
- Fix missing primitive aliases (split, length, merge) in bootstrap_py.py

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

shared/sx/ref/bootstrap_js.py

@@ -376,6 +376,11 @@ class JSEmitter:
             "event-source-listen": "eventSourceListen",
             "bind-boost-link": "bindBoostLink",
             "bind-boost-form": "bindBoostForm",
+            "bind-client-route-link": "bindClientRouteLink",
+            "bind-client-route-click": "bindClientRouteClick",
+            "try-client-route": "tryClientRoute",
+            "try-eval-content": "tryEvalContent",
+            "url-pathname": "urlPathname",
             "bind-inline-handler": "bindInlineHandler",
             "bind-preload": "bindPreload",
             "mark-processed!": "markProcessed",
@@ -490,6 +495,9 @@ class JSEmitter:
             "log-info": "logInfo",
             "log-parse-error": "logParseError",
             "parse-and-load-style-dict": "parseAndLoadStyleDict",
+            "_page-routes": "_pageRoutes",
+            "process-page-scripts": "processPageScripts",
+            "query-page-scripts": "queryPageScripts",
             # deps.sx
             "scan-refs": "scanRefs",
             "scan-refs-walk": "scanRefsWalk",
@@ -513,6 +521,14 @@ class JSEmitter:
             "transitive-io-refs": "transitiveIoRefs",
             "compute-all-io-refs": "computeAllIoRefs",
             "component-pure?": "componentPure_p",
+            # router.sx
+            "split-path-segments": "splitPathSegments",
+            "make-route-segment": "makeRouteSegment",
+            "parse-route-pattern": "parseRoutePattern",
+            "match-route-segments": "matchRouteSegments",
+            "match-route": "matchRoute",
+            "find-matching-route": "findMatchingRoute",
+            "for-each-indexed": "forEachIndexed",
         }
         if name in RENAMES:
             return RENAMES[name]
@@ -1026,6 +1042,7 @@ ADAPTER_DEPS = {
 
 SPEC_MODULES = {
     "deps": ("deps.sx", "deps (component dependency analysis)"),
+    "router": ("router.sx", "router (client-side route matching)"),
 }
 
 
@@ -1170,6 +1187,7 @@ def compile_ref_to_js(
                 raise ValueError(f"Unknown spec module: {sm!r}. Valid: {', '.join(SPEC_MODULES)}")
             spec_mod_set.add(sm)
     has_deps = "deps" in spec_mod_set
+    has_router = "router" in spec_mod_set
 
     # Core files always included, then selected adapters, then spec modules
     sx_files = [
@@ -1256,7 +1274,7 @@ def compile_ref_to_js(
     parts.append(fixups_js(has_html, has_sx, has_dom))
     if has_continuations:
         parts.append(CONTINUATIONS_JS)
-    parts.append(public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_cssx, has_boot, has_parser, adapter_label, has_deps))
+    parts.append(public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_cssx, has_boot, has_parser, adapter_label, has_deps, has_router))
     parts.append(EPILOGUE)
     return "\n".join(parts)
 
@@ -2589,6 +2607,50 @@ PLATFORM_ORCHESTRATION_JS = """
     });
   }
 
+  // --- Client-side route bindings ---
+
+  function bindClientRouteClick(link, href, fallbackFn) {
+    link.addEventListener("click", function(e) {
+      e.preventDefault();
+      var pathname = urlPathname(href);
+      if (tryClientRoute(pathname)) {
+        try { history.pushState({ sxUrl: href, scrollY: window.scrollY }, "", href); } catch (err) {}
+        if (typeof window !== "undefined") window.scrollTo(0, 0);
+      } else {
+        logInfo("sx:route server " + pathname);
+        executeRequest(link, { method: "GET", url: href }).then(function() {
+          try { history.pushState({ sxUrl: href, scrollY: window.scrollY }, "", href); } catch (err) {}
+        });
+      }
+    });
+  }
+
+  function tryEvalContent(source, env) {
+    try {
+      var merged = merge(componentEnv);
+      if (env && !isNil(env)) {
+        var ks = Object.keys(env);
+        for (var i = 0; i < ks.length; i++) merged[ks[i]] = env[ks[i]];
+      }
+      return sxRenderWithEnv(source, merged);
+    } catch (e) {
+      return NIL;
+    }
+  }
+
+  function urlPathname(href) {
+    try {
+      return new URL(href, location.href).pathname;
+    } catch (e) {
+      // Fallback: strip query/hash
+      var idx = href.indexOf("?");
+      if (idx >= 0) href = href.substring(0, idx);
+      idx = href.indexOf("#");
+      if (idx >= 0) href = href.substring(0, idx);
+      return href;
+    }
+  }
+
   // --- Inline handlers ---
 
   function bindInlineHandler(el, eventName, body) {
@@ -2861,6 +2923,12 @@ PLATFORM_BOOT_JS = """
       document.querySelectorAll('script[type="text/sx-styles"]'));
   }
 
+  function queryPageScripts() {
+    if (!_hasDom) return [];
+    return Array.prototype.slice.call(
+      document.querySelectorAll('script[type="text/sx-pages"]'));
+  }
+
   // --- localStorage ---
 
   function localStorageGet(key) {
@@ -2968,7 +3036,7 @@ def fixups_js(has_html, has_sx, has_dom):
     return "\n".join(lines)
 
 
-def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_cssx, has_boot, has_parser, adapter_label, has_deps=False):
+def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_cssx, has_boot, has_parser, adapter_label, has_deps=False, has_router=False):
     # Parser: use compiled sxParse from parser.sx, or inline a minimal fallback
     if has_parser:
         parser = '''
@@ -3101,6 +3169,11 @@ def public_api_js(has_html, has_sx, has_dom, has_engine, has_orch, has_cssx, has
         api_lines.append('    transitiveIoRefs: transitiveIoRefs,')
         api_lines.append('    computeAllIoRefs: computeAllIoRefs,')
         api_lines.append('    componentPure_p: componentPure_p,')
+    if has_router:
+        api_lines.append('    splitPathSegments: splitPathSegments,')
+        api_lines.append('    parseRoutePattern: parseRoutePattern,')
+        api_lines.append('    matchRoute: matchRoute,')
+        api_lines.append('    findMatchingRoute: findMatchingRoute,')
 
     api_lines.append(f'    _version: "{version}"')
     api_lines.append('  };')