GUEST: step 3 — lib/guest/lex.sx character-class + token primitives

Extracted shared tokeniser primitives:
- Char-class predicates: lex-digit?, lex-hex-digit?, lex-alpha?
  (alias lex-letter?), lex-alnum?, lex-ident-start?, lex-ident-char?,
  lex-space? (no newline), lex-whitespace? (incl newline). All nil-safe.
- Token record: lex-make-token, lex-make-token-spanning, accessors.

Ported lib/lua/tokenizer.sx and lib/tcl/tokenizer.sx — 7 lua and 5 tcl
predicate definitions collapsed into prefix-rename calls that alias
lua-/tcl- names to lex- primitives. Test scripts (lua/test.sh,
tcl/test.sh, tcl/conformance.sh) load lib/guest/lex.sx and prefix.sx
before the per-language tokenizer.

Verification:
- lua/test.sh: 185/185 = baseline
- tcl/test.sh: 342/342 (parse 67 + eval 169 + error 39 + namespace 22
                       + coro 20 + idiom 25)
- tcl/conformance.sh: 3/4 = baseline (event-loop failure is pre-existing)

Two consumers verified — step complete.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/lua/test.sh

@@ -28,6 +28,8 @@ trap "rm -f $TMPFILE" EXIT
 
 cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1)
+(load "lib/guest/lex.sx")
+(load "lib/guest/prefix.sx")
 (load "lib/lua/tokenizer.sx")
 (epoch 2)
 (load "lib/lua/parser.sx")

lib/lua/tokenizer.sx

@@ -1,31 +1,12 @@
-(define lua-make-token (fn (type value pos) {:pos pos :value value :type type}))
+(prefix-rename "lua-"
+  '((make-token   lex-make-token)
+    (digit?       lex-digit?)
+    (hex-digit?   lex-hex-digit?)
+    (letter?      lex-alpha?)
+    (ident-start? lex-ident-start?)
+    (ident-char?  lex-ident-char?)
+    (ws?          lex-whitespace?)))
 
-(define lua-digit? (fn (c) (and (not (= c nil)) (>= c "0") (<= c "9"))))
-
-(define
-  lua-hex-digit?
-  (fn
-    (c)
-    (and
-      (not (= c nil))
-      (or
-        (lua-digit? c)
-        (and (>= c "a") (<= c "f"))
-        (and (>= c "A") (<= c "F"))))))
-
-(define
-  lua-letter?
-  (fn
-    (c)
-    (and
-      (not (= c nil))
-      (or (and (>= c "a") (<= c "z")) (and (>= c "A") (<= c "Z"))))))
-
-(define lua-ident-start? (fn (c) (or (lua-letter? c) (= c "_"))))
-
-(define lua-ident-char? (fn (c) (or (lua-ident-start? c) (lua-digit? c))))
-
-(define lua-ws? (fn (c) (or (= c " ") (= c "\t") (= c "\n") (= c "\r"))))
 
 (define
   lua-keywords