Lake demo: page path in copyright updates across navigation morphs

The ~sx-header island now shows the current page path (faded, after
the copyright) inside the copyright lake. Navigate between pages:
the path text updates via server-driven lake morph while the reactive
colour-cycling signal persists. Subtle visible proof of L2-3.

Also fixes Island &key param serialization in component-source helper.

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

sx/sx/layouts.sx

@@ -15,7 +15,7 @@
 ;; The server can update these during navigation morphs without disturbing
 ;; the reactive colour-cycling state. This is Level 2-3: the water (server
 ;; content) flows through the island, around the rocks (reactive signals).
-(defisland ~sx-header ()
+(defisland ~sx-header (&key path)
   (let ((families (list "violet" "rose" "blue" "emerald" "amber" "cyan" "red" "teal" "pink" "indigo"))
         (idx (signal 0))
         (shade (signal 500))
@@ -45,10 +45,16 @@
               (reset! shade (+ 400 (* (mod (* (deref idx) 137) 5) 50))))))
           "reactive")
         " hypermedia")
-      ;; Lake: server can update the copyright
+      ;; Lake: server morphs this on every navigation — the path updates
+      ;; while the reactive colour above persists. Visible proof that
+      ;; server content flows through the island without disturbing signals.
       (lake :id "copyright"
         (p :style (cssx (:text (colour "stone" 400) (size "xs")))
-          "© Giles Bradshaw 2026")))))
+          "© Giles Bradshaw 2026"
+          (when path
+            (span :style (str (cssx (:text (colour "stone" 300) (size "xs")))
+                              "margin-left:0.5em;")
+              (str "· " path))))))))
 
 ;; @css grid grid-cols-3
 
@@ -115,7 +121,7 @@
          (trail-len (len trail)))
     (<>
       (div :id "sx-nav" :class "mb-6"
-        (~sx-header)
+        (~sx-header :path (or path "/"))
         ;; Sibling arrows for EVERY level in the trail
         ;; Last row (leaf) gets is-leaf for larger current page title
         (map-indexed (fn (i crumb)

sx/sxc/pages/helpers.py

@@ -44,7 +44,7 @@ def _component_source(name: str) -> str:
 
     comp = get_component_env().get(name)
     if isinstance(comp, Island):
-        param_strs = list(comp.params)
+        param_strs = (["&key"] + list(comp.params)) if comp.params else []
         if comp.has_children:
             param_strs.extend(["&rest", "children"])
         params_sx = "(" + " ".join(param_strs) + ")"