go: parse.sx scaffold — primary expressions + Go precedence table + 17 tests [consumes-pratt consumes-ast]

Starts Phase 2. lib/go/parse.sx defines:
  * go-precedence-table — Go's five operator-precedence levels in the
    (NAME PREC ASSOC) entry shape from lib/guest/pratt.sx, ready for the
    binary-operator iteration to consume via pratt-op-lookup.
  * go-parse(src) — tokenises and parses ONE primary expression: int,
    float, imag, string, rune literals become (ast-literal VALUE);
    identifiers become (ast-var NAME). Built directly on lib/guest/ast.sx
    constructors — no intermediate AST shape.

Conformance.sh extended to load lib/guest/{ast,pratt}.sx and run the
new parse suite. Scoreboard cleanup: drop the "pending" parse row since
the suite is now real.

parse 17/17 (lex still 129/129). Total 146/146.

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

lib/go/tests/parse.sx

@@ -0,0 +1,43 @@
+;; Go parser tests.
+
+(define go-parse-test-count 0)
+(define go-parse-test-pass 0)
+(define go-parse-test-fails (list))
+
+(define
+  go-parse-test
+  (fn
+    (name actual expected)
+    (set! go-parse-test-count (+ go-parse-test-count 1))
+    (if
+      (= actual expected)
+      (set! go-parse-test-pass (+ go-parse-test-pass 1))
+      (append! go-parse-test-fails {:name name :expected expected :actual actual}))))
+
+;; ── primary: literals ─────────────────────────────────────────────
+(go-parse-test "int literal" (go-parse "42") (ast-literal "42"))
+(go-parse-test "zero literal" (go-parse "0") (ast-literal "0"))
+(go-parse-test "hex literal" (go-parse "0xFF") (ast-literal "0xFF"))
+(go-parse-test "float literal" (go-parse "3.14") (ast-literal "3.14"))
+(go-parse-test "leading-dot float" (go-parse ".5") (ast-literal ".5"))
+(go-parse-test "exponent float" (go-parse "1e10") (ast-literal "1e10"))
+(go-parse-test "imag literal" (go-parse "2i") (ast-literal "2i"))
+(go-parse-test "string literal" (go-parse "\"hi\"") (ast-literal "hi"))
+(go-parse-test "empty string" (go-parse "\"\"") (ast-literal ""))
+(go-parse-test "raw string" (go-parse "`a\nb`") (ast-literal "a\nb"))
+(go-parse-test "rune literal" (go-parse "'a'") (ast-literal "a"))
+
+;; ── primary: identifiers ──────────────────────────────────────────
+(go-parse-test "ident: simple" (go-parse "x") (ast-var "x"))
+(go-parse-test "ident: underscore" (go-parse "_foo") (ast-var "_foo"))
+(go-parse-test "ident: mixed case" (go-parse "fooBar") (ast-var "fooBar"))
+(go-parse-test "ident: with digit" (go-parse "x123") (ast-var "x123"))
+
+;; ── primary: non-primary returns nil ──────────────────────────────
+(go-parse-test "non-primary: '+'" (go-parse "+") nil)
+(go-parse-test "non-primary: empty" (go-parse "") nil)
+
+;; ── report ────────────────────────────────────────────────────────
+(define
+  go-parse-test-summary
+  (str "parse " go-parse-test-pass "/" go-parse-test-count))