refactor(ffi-linkage): Phase 9.2a — rename runtime-class TYPE names → Runtime* (Decision 5)

Mechanical, collision-free PascalCase renames (object-model axis, not linkage):
ForeignClassDecl→RuntimeClassDecl, ForeignMethodDecl→RuntimeMethodDecl,
ForeignClassMember→RuntimeClassMember, ForeignFieldDecl→RuntimeFieldDecl,
ForeignRuntime→RuntimeKind, ForeignClassPrefix→RuntimeClassPrefix. Snapshot-neutral;
suite green (646/444). Remaining 9.2: snake_case state (foreign_class_map,
current_foreign_class, foreign_path [coupled to .sx hooks], the foreign_class_decl
union variant) + the parse/lower/resolve fn names + ForeignClassDecl.is_foreign flag.

src/ast.zig

@@ -93,7 +93,7 @@ pub const Node = struct {
         protocol_decl: ProtocolDecl,
         impl_block: ImplBlock,
         ffi_intrinsic_call: FfiIntrinsicCall,
-        foreign_class_decl: ForeignClassDecl,
+        foreign_class_decl: RuntimeClassDecl,
         jni_env_block: JniEnvBlock,
 
         pub fn declName(self: Data) ?[]const u8 {
@@ -836,7 +836,7 @@ pub const ProtocolDecl = struct {
     source_file: ?[]const u8 = null,
 };
 
-pub const ForeignRuntime = enum {
+pub const RuntimeKind = enum {
     jni_class,
     jni_interface,
     objc_class,
@@ -846,7 +846,7 @@ pub const ForeignRuntime = enum {
     swift_protocol,
 };
 
-pub const ForeignMethodDecl = struct {
+pub const RuntimeMethodDecl = struct {
     name: []const u8,
     params: []const *Node, // type_expr nodes — first is `*Self` for instance methods
     param_names: []const []const u8,
@@ -862,7 +862,7 @@ pub const ForeignMethodDecl = struct {
     body: ?*Node = null, // sx-side implementation (defined-class only). null = `;`-terminated decl referencing inherited / external method.
 };
 
-pub const ForeignFieldDecl = struct {
+pub const RuntimeFieldDecl = struct {
     name: []const u8,
     field_type: *Node, // type_expr node
     /// True iff the declaration carries a `#property[(...)]` directive
@@ -876,18 +876,18 @@ pub const ForeignFieldDecl = struct {
     property_modifiers: []const []const u8 = &.{},
 };
 
-pub const ForeignClassMember = union(enum) {
-    method: ForeignMethodDecl,
-    field: ForeignFieldDecl, // JNI runtime only (sema-checked in later step)
+pub const RuntimeClassMember = union(enum) {
+    method: RuntimeMethodDecl,
+    field: RuntimeFieldDecl, // JNI runtime only (sema-checked in later step)
     extends: []const u8, // sx-side alias name (right of `#extends`)
     implements: []const u8, // sx-side alias name (right of `#implements`)
 };
 
-pub const ForeignClassDecl = struct {
+pub const RuntimeClassDecl = struct {
     name: []const u8, // sx-side alias (left of `::`)
     foreign_path: []const u8, // directive arg: "java/path/Foo" / "NSString" / "Foundation.URL"
-    runtime: ForeignRuntime,
-    members: []const ForeignClassMember = &.{},
+    runtime: RuntimeKind,
+    members: []const RuntimeClassMember = &.{},
     is_foreign: bool = false, // `#foreign #...` prefix — class is provided by the foreign runtime; we only reference it
     is_main: bool = false, // `#jni_main` / `#objc_main` — class is the launchable entry (Activity / UIApplicationDelegate / ...)
     /// True when the sx-side alias NAME was a backtick raw identifier — exempt