go: lex.sx — hex/octal/binary integer literals + underscores, +14 tests [consumes-lex]

Adds prefixed integer forms per Go spec § Integer literals:
0x.. / 0X.. (hex), 0b.. / 0B.. (binary), 0o.. / 0O.. (octal),
legacy 0123 octal also accepted. Underscores allowed between digits
in any run; lexer is permissive (parser/types phase can enforce
strict placement).

Dispatch lives in gl-read-number! against the first 1-2 chars;
hex digit run consumes lex-hex-digit? from lib/guest/lex.sx. Octal
and binary use local gl-oct-digit?/gl-bin-digit? — narrow enough
that promoting them to the kit is premature.

lex 92/92.

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

lib/go/tests/lex.sx

@@ -68,12 +68,43 @@
 (go-test "kw: type" (tok-types "type") (list "keyword" "eof"))
 (go-test "kw: var" (tok-types "var") (list "keyword" "eof"))
 
-;; ── integer literals ──────────────────────────────────────────────
+;; ── integer literals — decimal ────────────────────────────────────
 (go-test "int: zero" (tok-values "0") (list "0" "\n" nil))
 (go-test "int: small" (tok-values "42") (list "42" "\n" nil))
 (go-test "int: bigger" (tok-values "123456") (list "123456" "\n" nil))
 (go-test "int: type" (tok-types "42") (list "int" "semi" "eof"))
 
+;; ── integer literals — prefixed + underscores (Go spec § Integer literals)
+(go-test "int: hex lower" (tok-values "0x1f") (list "0x1f" "\n" nil))
+(go-test "int: hex upper-x" (tok-values "0X1F") (list "0X1F" "\n" nil))
+(go-test
+  "int: hex mixed digits"
+  (tok-values "0xDEADbeef")
+  (list "0xDEADbeef" "\n" nil))
+(go-test "int: binary lower" (tok-values "0b1010") (list "0b1010" "\n" nil))
+(go-test "int: binary upper" (tok-values "0B1101") (list "0B1101" "\n" nil))
+(go-test "int: octal modern" (tok-values "0o755") (list "0o755" "\n" nil))
+(go-test "int: octal upper" (tok-values "0O17") (list "0O17" "\n" nil))
+(go-test "int: octal legacy" (tok-values "0755") (list "0755" "\n" nil))
+(go-test "int: hex type" (tok-types "0x1F") (list "int" "semi" "eof"))
+(go-test "int: bin type" (tok-types "0b101") (list "int" "semi" "eof"))
+(go-test
+  "int: dec underscore"
+  (tok-values "1_000_000")
+  (list "1_000_000" "\n" nil))
+(go-test
+  "int: hex underscore"
+  (tok-values "0xDEAD_BEEF")
+  (list "0xDEAD_BEEF" "\n" nil))
+(go-test
+  "int: bin underscore"
+  (tok-values "0b1010_1010")
+  (list "0b1010_1010" "\n" nil))
+(go-test
+  "int: hex then +"
+  (tok-types "0xFF + 1")
+  (list "int" "op" "int" "semi" "eof"))
+
 ;; ── string literals ───────────────────────────────────────────────
 (go-test "string: empty" (tok-values "\"\"") (list "" "\n" nil))
 (go-test "string: hello" (tok-values "\"hello\"") (list "hello" "\n" nil))