fix(render3d, runtime): a glTF document is freed whole, layouts found by number, block records reused

- Json.free_all (value_free_all): a parsed tree's nodes, lists and strings. render3d frees each
  glTF document that way at the next load; the names kept out of it are copies (a primitive's
  material, a skin's joints, an animation clip's name in ludic.anim) - a model's strings were
  ~640 KB left behind per load
- jp_number made a digits list per decimal in a document and never freed it
- gvk_layout_id matches a mesh's layout as numbers in a scratch made once, against the layouts
  known end to end; a new mesh no longer builds a key string
- gvk_mem_new puts a new block into the record of one given back rather than appending, so a
  buffer made again every few frames no longer grows the block lists

steady.ludic adds a glTF parsed and freed whole 200 times: 0 bytes (38,400 before the digits fix),
beside the buffer path and the frame, still 0. A model loaded and let go still keeps ~2 KB a round
(texture and buffer handles are not reused yet); it is bounded at 8 KB a round.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

runtime/native/namespaces.ludic

@@ -489,6 +489,7 @@ namespace Json {
   alias encode(value) = json_encode
   alias parse(text) = json_parse
   alias free(value) = json_free
+  alias free_all(value) = json_free_all
 }
 namespace Xml {
   alias parse(text) = xml_parse

runtime/native/value.ludic

@@ -384,6 +384,21 @@ function value_free(v: Val) -> void {
   free(v)
 }
 function json_free(v: Val) -> void { value_free(v) }
+# ... and its strings too - every string value and object key the parser made - for a tree whose
+# reader copied what it keeps (render3d's glTF documents): a parse left otherwise gives back the
+# nodes and keeps every name, ~640 KB a model
+function value_free_all(v: Val) -> void {
+  if v == null { return }
+  if v.tag == 4 and v.txt != null { free(v.txt) }
+  if v.kids != null {
+    for i in 0 .. len(v.kids) { value_free_all(v.kids[i]) }
+    if v.keys != null { for i in 0 .. len(v.keys) { if v.keys[i] != null { free(v.keys[i]) } } }
+    free(v.kids)
+    free(v.keys)
+  }
+  free(v)
+}
+function json_free_all(v: Val) -> void { value_free_all(v) }
 
 function jp_value(p: JP) -> Val {
   jp_skip_ws(p)
@@ -467,6 +482,7 @@ function jp_number(p: JP) -> Val {
       frac = (digits[di] * 65536 + frac) / 10
       di -= 1
     }
+    free(digits)                                 # one list per decimal in the document, never given back
     var raw = ip * 65536 + frac
     raw = jp_exponent(p, raw)
     if neg != 0 { raw = -raw }