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/tcl/conformance.sh

@@ -63,6 +63,8 @@ for tcl_file in "${TCL_FILES[@]}"; do
   # Build epoch input using quoted heredoc for static parts; helper path via variable
   cat > "$tmpfile" << EPOCHS
 (epoch 1)
+(load "lib/guest/lex.sx")
+(load "lib/guest/prefix.sx")
 (load "lib/tcl/tokenizer.sx")
 (epoch 2)
 (load "lib/tcl/parser.sx")

lib/tcl/test.sh

@@ -33,6 +33,8 @@ HELPER_EOF
 
 cat > "$TMPFILE" << EPOCHS
 (epoch 1)
+(load "lib/guest/lex.sx")
+(load "lib/guest/prefix.sx")
 (load "lib/tcl/tokenizer.sx")
 (epoch 2)
 (load "lib/tcl/parser.sx")

lib/tcl/tokenizer.sx

@@ -1,19 +1,10 @@
-(define tcl-ws? (fn (c) (or (= c " ") (= c "\t") (= c "\r"))))
+(prefix-rename "tcl-"
+  '((ws?          lex-space?)
+    (alpha?       lex-alpha?)
+    (digit?       lex-digit?)
+    (ident-start? lex-ident-start?)
+    (ident-char?  lex-ident-char?)))
 
-(define tcl-alpha?
-  (fn (c)
-    (and
-      (not (= c nil))
-      (or (and (>= c "a") (<= c "z")) (and (>= c "A") (<= c "Z"))))))
-
-(define tcl-digit?
-  (fn (c) (and (not (= c nil)) (>= c "0") (<= c "9"))))
-
-(define tcl-ident-start?
-  (fn (c) (or (tcl-alpha? c) (= c "_"))))
-
-(define tcl-ident-char?
-  (fn (c) (or (tcl-ident-start? c) (tcl-digit? c))))
 
 (define tcl-tokenize
   (fn (src)