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/scoreboard.json

@@ -1,9 +1,9 @@
 {
   "language": "go",
-  "total_pass": 78,
-  "total": 78,
+  "total_pass": 92,
+  "total": 92,
   "suites": [
-    {"name":"lex","pass":78,"total":78,"status":"ok"},
+    {"name":"lex","pass":92,"total":92,"status":"ok"},
     {"name":"parse","pass":0,"total":0,"status":"pending"},
     {"name":"types","pass":0,"total":0,"status":"pending"},
     {"name":"eval","pass":0,"total":0,"status":"pending"},