Cache sx component definitions in localStorage across page loads

Server computes SHA-256 hash of all component source at startup.
Client signals its cached hash via cookie (sx-comp-hash). On full
page load: cookie match → server sends empty script tag with just
the hash; mismatch → sends full source. Client loads from
localStorage on hit, parses inline + caches on miss.

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

shared/sx/jinja_bridge.py

@@ -21,6 +21,7 @@ Setup::
 from __future__ import annotations
 
 import glob
+import hashlib
 import os
 from typing import Any
 
@@ -37,12 +38,42 @@ from .html import render as html_render, _render_component
 # definition files or calling register_components().
 _COMPONENT_ENV: dict[str, Any] = {}
 
+# SHA-256 hash (12 hex chars) of all component definitions — used for
+# client-side localStorage caching.
+_COMPONENT_HASH: str = ""
+
 
 def get_component_env() -> dict[str, Any]:
     """Return the shared component environment."""
     return _COMPONENT_ENV
 
 
+def get_component_hash() -> str:
+    """Return the current component definitions hash."""
+    return _COMPONENT_HASH
+
+
+def _compute_component_hash() -> None:
+    """Recompute _COMPONENT_HASH from all registered Component definitions."""
+    global _COMPONENT_HASH
+    from .parser import serialize
+    parts = []
+    for key in sorted(_COMPONENT_ENV):
+        val = _COMPONENT_ENV[key]
+        if isinstance(val, Component):
+            param_strs = ["&key"] + list(val.params)
+            if val.has_children:
+                param_strs.extend(["&rest", "children"])
+            params_sx = "(" + " ".join(param_strs) + ")"
+            body_sx = serialize(val.body)
+            parts.append(f"(defcomp ~{val.name} {params_sx} {body_sx})")
+    if parts:
+        digest = hashlib.sha256("\n".join(parts).encode()).hexdigest()[:12]
+        _COMPONENT_HASH = digest
+    else:
+        _COMPONENT_HASH = ""
+
+
 def load_sx_dir(directory: str) -> None:
     """Load all .sx files from a directory and register components."""
     for filepath in sorted(
@@ -132,6 +163,8 @@ def register_components(sx_source: str) -> None:
                 all_classes = scan_classes_from_sx(sx_source)
             val.css_classes = set(all_classes)
 
+    _compute_component_hash()
+
 
 # ---------------------------------------------------------------------------
 # sx() — render s-expression from Jinja template