go: lex.sx — raw string literals (backtick) + 9 tests [nothing]

Adds Go raw string literals per Go spec § String literals:
backtick-delimited, no escape processing, may span multiple
lines, '\r' chars discarded from the value.

gl-read-raw-string! mirrors gl-read-string! but skips escape
handling and the \r filter. scan! routes the leading backtick
to it; emits "string" type (same as interpreted strings — no
need to distinguish at parse/type time).

lex 123/123.

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

lib/go/lex.sx

@@ -10,7 +10,7 @@
 ;;               legacy 0123 octal; underscores between digits allowed)
 ;;   "float"   — decimal float literals (3.14, .5, 1., 1e10, 1.5e-3, 1E5)
 ;;   "imag"    — imaginary literals (2i, 3.14i, 1e2i)
-;;   "string"  — interpreted string literals "..."
+;;   "string"  — interpreted string literals "..." OR raw string literals `...`
 ;;   "rune"    — rune literals 'x' (single char + simple escapes)
 ;;   "op"      — operators & punctuation; :value is the literal text
 ;;   "semi"    — explicit ';' or auto-inserted (Go spec § Semicolons)
@@ -253,6 +253,30 @@
                     (gl-string-loop)))))
             (gl-string-loop)
             (join "" chars))))
+      (define
+        gl-read-raw-string!
+        (fn
+          ()
+          (gl-advance! 1)
+          (let
+            ((chars (list)))
+            (define
+              gl-raw-loop
+              (fn
+                ()
+                (cond
+                  (>= pos src-len)
+                  nil
+                  (= (gl-cur) "`")
+                  (gl-advance! 1)
+                  (= (gl-cur) "\r")
+                  (do (gl-advance! 1) (gl-raw-loop))
+                  :else (do
+                    (append! chars (gl-cur))
+                    (gl-advance! 1)
+                    (gl-raw-loop)))))
+            (gl-raw-loop)
+            (join "" chars))))
       (define
         gl-read-rune!
         (fn
@@ -426,6 +450,11 @@
               ((start pos) (v (gl-read-string!)))
               (gl-emit! "string" v start)
               (gl-scan!))
+            (= (gl-cur) "`")
+            (let
+              ((start pos) (v (gl-read-raw-string!)))
+              (gl-emit! "string" v start)
+              (gl-scan!))
             (= (gl-cur) "'")
             (let
               ((start pos) (v (gl-read-rune!)))