Fix component body serialization: capture ALL body expressions

defcomp/defisland with multi-expression bodies (let, letrec,
freeze-scope, effect) had only the LAST expression stored as body.
The browser received a truncated defisland missing let/letrec/signal
bindings, causing "Undefined symbol: code-tokens" on hydration.

Fix: body_exprs = expr[body_start:], wrapped in (begin ...) if
multiple. Also clear stale pickle cache on code changes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/sx/jinja_bridge.py

@@ -52,6 +52,11 @@ _COMPONENT_HASH: str = ""
 # available for client-side evaluation (e.g. cssx colour/spacing functions).
 _CLIENT_LIBRARY_SOURCES: list[str] = []
 
+# Raw source text per component name — used to send the ORIGINAL source
+# to the browser instead of re-serializing the evaluated AST (which loses
+# let/letrec/signal bindings that the client needs for hydration).
+_COMPONENT_RAW_SOURCE: dict[str, str] = {}
+
 
 def get_component_env() -> dict[str, Any]:
     """Return the shared component environment."""
@@ -456,10 +461,19 @@ def register_components(sx_source: str, *, _defer_postprocess: bool = False) ->
             if name and expr[0].name in ("defcomp", "defisland"):
                 params, has_children = _parse_defcomp_params(expr[2] if len(expr) > 3 else [])
                 cls = Island if expr[0].name == "defisland" else Component
+                # Body may be multiple expressions (let, letrec, freeze-scope, etc.)
+                # Skip name + params; also skip :effects keyword pair if present
+                body_start = 3
+                if (len(expr) > 4
+                    and hasattr(expr[3], 'name')
+                    and isinstance(expr[3], Keyword)):
+                    body_start = 5  # skip :effects [list]
+                body_exprs = expr[body_start:]
+                body = body_exprs[0] if len(body_exprs) == 1 else [Symbol("begin")] + body_exprs
                 _COMPONENT_ENV[name] = cls(
                     name=name.lstrip("~"),
                     params=params, has_children=has_children,
-                    body=expr[-1], closure={},
+                    body=body, closure={},
                 )
 
     # Pre-scan CSS classes for newly registered components.