Phase 7e: polymorphic print(x) + str(x) (retire print_int/print_str)

One `print` instead of two C-style names: `print(x)` writes an int OR a string
followed by a newline, dispatching on the operand type (int -> %d, string ->
%s). `print(int)` emits byte-identically to the old print_int, so every existing
call and every smoke-test output is unchanged.

print_str was only ever the raw IR-to-stdout dump in ir_flush (no newline), which
is not "printing a line" — so it now uses file_write to a new file_stdout()
stream, keeping the emitted IR byte-for-byte identical. That frees `print` to
have consistent always-newline semantics.

Two reseeds: (A) add print + str + file_stdout keeping the intrinsics; (B)
migrate the 61 print_int calls to print, ir_flush to file_write(file_stdout()),
and delete print_int/print_str (+ the now-dead @.fmt_str). str(x) (the
interpolation converter from 7d) is now also a documented standalone builtin.

Vocabulary: print/str/file_stdout in, print_int/print_str out (ludic_syntax.h,
grammar, LudicTokens.kt). LANGUAGE.md updated. Reseeded (22551 lines); C-free
fixpoint holds; goldens identical; 18/18; vocab + doc-fences clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

LANGUAGE.md

@@ -403,9 +403,9 @@ handler Share phase Update {
   let a = new Tok
   let b = a              # b and a are the SAME object
   b.kind = 9
-  print_int(a.kind)      # 9
+  print(a.kind)      # 9
   bump(a)                # the mutation is visible to the caller
-  print_int(a.kind)      # 10
+  print(a.kind)      # 10
 }
 ```
 
@@ -417,7 +417,7 @@ handler Walk phase Update {
   let a = new Tok
   let b = new Tok
   a.next = b
-  print_int(a.next.kind)
+  print(a.next.kind)
   a.next.kind = 42       # chains on the left of an assignment too
 }
 ```
@@ -445,7 +445,7 @@ header never moves, an append is visible to everything holding that slice.
 handler Collect phase Update {
   let toks = new []Tok
   push(toks, new Tok)
-  for i in 0 .. len(toks) { print_int(toks[i].kind) }
+  for i in 0 .. len(toks) { print(toks[i].kind) }
 }
 ```
 
@@ -626,7 +626,8 @@ literal; test any pointer/record/slice with `x == null` / `x != null` (an unset
 # state     reg(i)->int   set_reg(i,v)     (64 integer resources shared by handlers)
 # entity    self()->entity
 # save      save()   load()->bool         (binary snapshot of the whole ECS World)
-# control   quit()   print_int(i)
+# control   quit()   print(x)          (a value + newline)
+# convert   str(x) -> str            (int/bool/fixed -> text)
 # process   os_argc()->int   os_arg(i)->str        (the command line; argv[0] included)
 #           file_stderr()->ptr                     (a handle for file_write, off stdout)
 ```