ludic ui-preview: ludic.ui components previewed for a studio over stdio (R5)

A prebuilt tool, bin/ludic-ui-preview (built by ludic-dev build, shipped beside ludic-lsp, run as
`ludic ui-preview [--font DIR]`): ludic.ui with a backend that records every draw call as a line,
and mock component classes the studio describes (load / model / calls). frame t runs ui_show at
interface time t; text is measured on the CPU with the game's font.json metrics; locale goes
through ludic.i18n; tree / box / rules inspect the frame. No game code, no GPU, no network. The wire
protocol is frozen as tools/ui-preview/protocol-v1.md; smoke.txt is a transcript to run.

ludic.ui gains, all additive: UiClass.make_of, UiBackend.said / emitted, UiRule.text / at (with
comment line breaks kept so rule lines count true, and a class's styles read under its .lss path),
and ui_root, ui_find, ui_rules_of, ui_rule_value, ui_building, ui_class, ui_class_load,
ui_file_forget, ui_errors_clear; ui_nine_cuts_into exported.

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

tools/ui-preview/out.ludic

@@ -0,0 +1,78 @@
+# out.ludic - the reply stream: lines written into a buffer made once and grown when a frame needs
+# more, then written and flushed whole, so a draw list makes no string per primitive
+property PvOut {
+  p: pointer = null
+  n: int = 0
+  cap: int = 0
+}
+extern function fflush(f: pointer) -> int = "fflush"
+function pv_room(o: PvOut, more: int) -> void {
+  if o.n + more + 1 <= o.cap { return }
+  var cap = o.cap * 2
+  if cap < 65536 { cap = 65536 }
+  while cap < o.n + more + 1 { cap = cap * 2 }
+  var q: pointer = null
+  unsafe {
+    q = bytes(cap)
+    for i in 0 .. o.n { q[i] = o.p[i] }
+    if o.p != null { free(o.p) }
+  }
+  o.p = q
+  o.cap = cap
+}
+function pv_byte(o: PvOut, c: int) -> void {
+  pv_room(o, 1)
+  unsafe { o.p[o.n] = c }
+  o.n += 1
+}
+# text as it is (a word of the protocol)
+function pv_s(o: PvOut, s: string) -> void {
+  let k = len(s)
+  pv_room(o, k)
+  unsafe {
+    for i in 0 .. k { o.p[o.n + i] = s[i] }
+  }
+  o.n += k
+}
+# a space, then a word
+function pv_w(o: PvOut, s: string) -> void {
+  pv_byte(o, 32)
+  pv_s(o, s)
+}
+# a space, then text as a JSON string: " and \ escaped, control bytes as \n \r \t or \u00XX, UTF-8 as is
+function pv_q(o: PvOut, s: string) -> void {
+  pv_byte(o, 32)
+  pv_byte(o, 34)
+  for i in 0 .. len(s) {
+    let c = s[i] & 255
+    if c == 34 or c == 92 {
+      pv_byte(o, 92)
+      pv_byte(o, c)
+    } else if c == 10 {
+      pv_s(o, "\\n")
+    } else if c == 13 {
+      pv_s(o, "\\r")
+    } else if c == 9 {
+      pv_s(o, "\\t")
+    } else if c < 32 {
+      pv_s(o, "\\u00")
+      pv_byte(o, pv_hexch(c / 16))
+      pv_byte(o, pv_hexch(c % 16))
+    } else { pv_byte(o, c) }
+  }
+  pv_byte(o, 34)
+}
+function pv_hexch(d: int) -> int {
+  if d < 10 { return 48 + d }
+  return 87 + d
+}
+# the line so far ends
+function pv_nl(o: PvOut) -> void { pv_byte(o, 10) }
+# everything buffered goes to stdout now, and the buffer is empty again
+function pv_flush(o: PvOut) -> void {
+  if o.n == 0 { return }
+  let f = file_stdout()
+  unsafe { file_write(f, o.p, o.n) }
+  fflush(f)
+  o.n = 0
+}