Add (param :as type) annotations to all fn/lambda params across SX spec

Extend the type annotation system from defcomp-only to fn/lambda params:
- Infrastructure: sf-lambda, py/js-collect-params-loop, and bootstrap_py.py
  now recognize (name :as type) in param lists, extracting just the name
- bootstrap_py.py: add _extract_param_name() helper, fix _emit_for_each_stmt
- 521 type annotations across 22 .sx spec files (eval, types, adapters,
  transpilers, engine, orchestration, deps, signals, router, prove, etc.)
- Zero behavioral change: annotations are metadata for static analysis only
- All bootstrappers (Python, JS, G1) pass, 81/81 spec tests pass

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/parser.sx

@@ -50,7 +50,7 @@
 ;; Returns a list of top-level AST expressions.
 
 (define sx-parse
-  (fn (source)
+  (fn ((source :as string))
     (let ((pos 0)
           (len-src (len source)))
 
@@ -170,7 +170,7 @@
       ;; -- Composite readers --
 
       (define read-list
-        (fn (close-ch)
+        (fn ((close-ch :as string))
           (let ((items (list)))
             (define read-list-loop
               (fn ()
@@ -352,11 +352,11 @@
 
 
 (define sx-serialize-dict
-  (fn (d)
+  (fn ((d :as dict))
     (str "{"
       (join " "
         (reduce
-          (fn (acc key)
+          (fn ((acc :as list) (key :as string))
             (concat acc (list (str ":" key) (sx-serialize (dict-get d key)))))
           (list)
           (keys d)))