content: fix ct-class-for-type for all block types (callout/media data round-trip) + 4 tests (731/731)

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

lib/content/tests/data.sx

@@ -6,6 +6,8 @@
 (content-bootstrap-markdown!)
 (content-bootstrap-section!)
 (content-bootstrap-table!)
+(content-bootstrap-callout!)
+(content-bootstrap-media!)
 
 ;; ── block->data shape ──
 (define h (mk-heading "h" 2 "Hi"))
@@ -73,6 +75,27 @@
   (table-headers (doc-find rtt "t"))
   (list "A" "B"))
 
+;; ── callout + media round-trip (regression: ct-class-for-type must know them) ──
+(define
+  dcm
+  (doc-append
+    (doc-append (doc-empty "d") (mk-callout "co" "warning" "careful"))
+    (mk-video "vid" "/clip.mp4")))
+(define rtcm (content/from-data (content/to-data dcm)))
+(content-test "rt callout+media render" (asHTML rtcm) (asHTML dcm))
+(content-test
+  "rt callout kind"
+  (str (blk-send (doc-find rtcm "co") "kind"))
+  "warning")
+(content-test
+  "rt media kind"
+  (str (blk-send (doc-find rtcm "vid") "kind"))
+  "video")
+(content-test
+  "rt callout+media types"
+  (doc-types rtcm)
+  (list "callout" "media"))
+
 ;; ── data is plain (no st-instance markers at top level) ──
 (define dat (content/to-data d))
 (content-test "data id field" (get dat :id) "post")