go: parse.sx — binary operators via Pratt precedence climbing + 9 tests [consumes-pratt]

gp-parse-expr / gp-pratt-loop implement classic Pratt climbing
against go-precedence-table (entry shape from lib/guest/pratt.sx).
The kit gives us pratt-op-lookup + accessors; the climbing loop
itself stays per-language (per kit header — Lua and Prolog have
opposite conventions).

Left-associative ops raise the right-recursion min by 1; right-
associative would keep prec. All Go binary operators are left-assoc.

AST shape: a binary node is emitted as
  (ast-app (ast-var OP) [LHS RHS])
— canonical ast-app rather than a Go-specific binary node, since a
future evaluator can recognise operator-named apps without losing
information.

Coverage: equal-prec left-to-right, * tighter than +, && tighter
than ||, comparison tighter than &&, long left-assoc chains, mixed
literal+ident operands.

parse 26/26, total 155/155.

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

lib/go/scoreboard.json

@@ -1,10 +1,10 @@
 {
   "language": "go",
-  "total_pass": 146,
-  "total": 146,
+  "total_pass": 155,
+  "total": 155,
   "suites": [
     {"name":"lex","pass":129,"total":129,"status":"ok"},
-    {"name":"parse","pass":17,"total":17,"status":"ok"},
+    {"name":"parse","pass":26,"total":26,"status":"ok"},
     {"name":"types","pass":0,"total":0,"status":"pending"},
     {"name":"eval","pass":0,"total":0,"status":"pending"},
     {"name":"runtime","pass":0,"total":0,"status":"pending"},