Add types.sx gradual type system spec module with 44 tests

Implements subtype checking, type inference, type narrowing, and
component call-site checking. All type logic is in types.sx (spec),
bootstrapped to every host. Adds test-types.sx with full coverage.

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

shared/sx/types.py

@@ -170,6 +170,7 @@ class Component:
     deps: set[str] = field(default_factory=set)        # transitive component deps (~names)
     io_refs: set[str] | None = None     # transitive IO primitive refs (None = not computed)
     affinity: str = "auto"    # "auto" | "client" | "server"
+    param_types: dict[str, Any] | None = None  # {param_name: type_expr} for gradual typing
 
     @property
     def is_pure(self) -> bool: