go: eval.sx — stmts + function application; recursive fib evaluates + 8 tests [nothing]

Phase 4 cont. go-eval-stmt dispatches on:
  :return       → wraps value in (:return-value V) sentinel
  :var-decl     → bind each NAME via go-eval-var-decl
  :short-decl   → bind each (:var NAME) lhs to corresponding expr value
  :assign       → immutable-env shadowing (true mutation deferred)
  :block        → run stmts via go-eval-block, propagating :return-value
  :if / :else   → cond-driven dispatch
  :func-decl    → bind name to (list :go-fn PARAMS BODY)
  else          → expression statement, evaluate for side effects

go-eval-call extends the CALLER's env with param-names → arg-values
(dynamic-scope-ish — closures don't capture lexical env yet), runs the
body block, catches :return-value and unwraps.

**Recursive fib(5) = 5 evaluates correctly.** Recursion works because
top-level func bindings are in the calling env before the recursive
call happens.

True lexical closures (let bind sees outer var; assignments visible to
nested funcs) need an env-cell model with mutation; deferred to a
later slice.

eval 33/33, total 410/410.

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

lib/go/scoreboard.json

@@ -1,12 +1,12 @@
 {
   "language": "go",
-  "total_pass": 402,
-  "total": 402,
+  "total_pass": 410,
+  "total": 410,
   "suites": [
     {"name":"lex","pass":129,"total":129,"status":"ok"},
     {"name":"parse","pass":176,"total":176,"status":"ok"},
     {"name":"types","pass":72,"total":72,"status":"ok"},
-    {"name":"eval","pass":25,"total":25,"status":"ok"},
+    {"name":"eval","pass":33,"total":33,"status":"ok"},
     {"name":"runtime","pass":0,"total":0,"status":"pending"},
     {"name":"stdlib","pass":0,"total":0,"status":"pending"},
     {"name":"e2e","pass":0,"total":0,"status":"pending"}