go: types.sx — call type-checking + 8 tests; recursive funcs now type [nothing]

Phase 3 cont. The expression-synth :app dispatch is now bifurcated:

  * go-is-binop-call? — head is :var with an operator name AND 2 args
    AND the operator is in one of the binop tables. Short-circuits to
    go-synth-binop as before.
  * Everything else routes to go-synth-call.

go-synth-call:
  1. Synth the callee. Must produce a (list :ty-func PARAMS RESULTS).
     Otherwise → (:type-error :not-callable TYPE).
  2. Arity-check args vs params. Mismatch → (:type-error :arity-mismatch).
  3. go-check-args-against: each arg assignable to corresponding param
     (untyped-constant flow works — `f(42)` accepts the untyped int
     into an int param).
  4. Result by count:
       0 results → (list :ty-void)
       1 result  → that result directly
       N results → (list :ty-tuple TYPES)   for multi-return

The recursive case lights up: go-check-func-decl binds the function
in its own body's ctx before checking. So:

  func fib(n int) int { return fib(n) + fib(n) }

now type-checks because `fib` resolves inside the body, synth-call
sees its `:ty-func` and verifies the recursive call. Multi-return
functions destructure into `:ty-tuple` which short-decl will need to
consume next iteration.

types 55/55, total 360/360.

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

lib/go/scoreboard.md

@@ -1,12 +1,12 @@
 # Go-on-SX Scoreboard
 
-**Total: 352 / 352 tests passing**
+**Total: 360 / 360 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
 | ✅ | lex | 129 | 129 |
 | ✅ | parse | 176 | 176 |
-| ✅ | types | 47 | 47 |
+| ✅ | types | 55 | 55 |
 | ⬜ | eval | 0 | 0 |
 | ⬜ | runtime | 0 | 0 |
 | ⬜ | stdlib | 0 | 0 |