content: id remapping / clone (clone.sx) + 10 tests (561/561)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/content/tests/clone.sx

@@ -0,0 +1,55 @@
+;; Extension — block id remapping / clone.
+
+(st-bootstrap-classes!)
+(content/bootstrap!)
+(content-bootstrap-section!)
+
+(define
+  d
+  (doc-append
+    (doc-append (doc-empty "d") (mk-heading "h" 1 "Title"))
+    (mk-section "s" (list (mk-text "a" "A") (mk-text "b" "B")))))
+
+;; ── prefix-ids rewrites every id in the tree ──
+(define p (content/prefix-ids d "x-"))
+(content-test "prefix top-level ids" (doc-ids p) (list "x-h" "x-s"))
+(content-test
+  "prefix tree-ids"
+  (doc-tree-ids p)
+  (list "x-h" "x-s" "x-a" "x-b"))
+(content-test "prefix immutable" (doc-tree-ids d) (list "h" "s" "a" "b"))
+(content-test "prefix preserves content" (asHTML p) (asHTML d))
+(content-test
+  "prefix preserves nested content"
+  (str (blk-send (doc-deep-find p "x-a") "text"))
+  "A")
+
+;; ── custom remap fn ──
+(define u (content/remap-ids d (fn (id) (str id "!"))))
+(content-test "remap suffix" (doc-tree-ids u) (list "h!" "s!" "a!" "b!"))
+
+;; ── collision-free composition ──
+(define
+  d2
+  (doc-append (doc-empty "d2") (mk-heading "h" 2 "Other")))
+(define
+  combined
+  (content/concat
+    (content/prefix-ids d "left-")
+    (content/prefix-ids d2 "right-")))
+(content-test
+  "combined ids unique"
+  (doc-tree-ids combined)
+  (list "left-h" "left-s" "left-a" "left-b" "right-h"))
+(content-test "combined validates" (content/valid? combined) true)
+;; without prefixing, the shared id "h" collides
+(content-test
+  "unprefixed collides"
+  (content/valid? (content/concat d d2))
+  false)
+
+;; ── render of combined ──
+(content-test
+  "combined render"
+  (asHTML combined)
+  "<h1>Title</h1><section><p>A</p><p>B</p></section><h2>Other</h2>")