Dynamic IO proxy: derive proxied primitives from component io_refs

Replace hardcoded IO primitive lists on both client and server with
data-driven registration. Page registry entries carry :io-deps (list
of IO primitive names) instead of :has-io boolean. Client registers
proxied IO on demand per page via registerIoDeps(). Server builds
allowlist from component analysis.

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

shared/sx/helpers.py

@@ -691,14 +691,17 @@ def _build_pages_sx(service: str) -> str:
             deps = components_needed(content_src, _COMPONENT_ENV)
         deps_sx = "(" + " ".join(_sx_literal(d) for d in sorted(deps)) + ")"
 
-        # Check if any dep component has IO refs (needs async rendering)
+        # Collect IO primitive names referenced by dep components
         from .types import Component as _Comp
-        has_io = "false"
+        io_deps: set[str] = set()
         for dep_name in deps:
             comp = _COMPONENT_ENV.get(dep_name)
             if isinstance(comp, _Comp) and comp.io_refs:
-                has_io = "true"
-                break
+                io_deps.update(comp.io_refs)
+        io_deps_sx = (
+            "(" + " ".join(_sx_literal(n) for n in sorted(io_deps)) + ")"
+            if io_deps else "()"
+        )
 
         # Build closure as SX dict
         closure_parts: list[str] = []
@@ -712,7 +715,7 @@ def _build_pages_sx(service: str) -> str:
             + " :path " + _sx_literal(page_def.path)
             + " :auth " + _sx_literal(auth)
             + " :has-data " + has_data
-            + " :has-io " + has_io
+            + " :io-deps " + io_deps_sx
             + " :content " + _sx_literal(content_src)
             + " :deps " + deps_sx
             + " :closure " + closure_sx + "}"