go: parse.sx — func type expressions (anonymous params) + 9 tests [nothing]

Adds Go func-type parsing to gp-parse-type:
  func()                  →  (list :ty-func () ())
  func() int              →  (list :ty-func () [int])
  func(int, string)       →  (list :ty-func [int string] ())
  func(int) string        →  (list :ty-func [int] [string])
  func() (int, error)     →  (list :ty-func () [int error])

gp-parse-func-type-params handles the param list inside (...);
gp-parse-func-type-results dispatches between bare single-return,
multi-return parenthesised list, or no return.

Anonymous-only — named params (`func(a int, b string)`) require a
different shape and are mainly needed for func DECLARATIONS, not for
pure func-type expressions in type position. Variadic ('...T')
deferred.

Covers nested cases: func returning func, chan of func, func with
pointer/slice operands.

parse 90/90, total 219/219.

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

lib/go/scoreboard.md

@@ -1,11 +1,11 @@
 # Go-on-SX Scoreboard
 
-**Total: 210 / 210 tests passing**
+**Total: 219 / 219 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
 | ✅ | lex | 129 | 129 |
-| ✅ | parse | 81 | 81 |
+| ✅ | parse | 90 | 90 |
 | ⬜ | types | 0 | 0 |
 | ⬜ | eval | 0 | 0 |
 | ⬜ | runtime | 0 | 0 |