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/parser.zig

@@ -1280,7 +1280,7 @@ pub const Parser = struct {
         } });
     }
 
-    fn foreignRuntimeForCurrent(self: *Parser) ?ast.ForeignRuntime {
+    fn foreignRuntimeForCurrent(self: *Parser) ?ast.RuntimeKind {
         return switch (self.current.tag) {
             .hash_jni_class => .jni_class,
             .hash_jni_interface => .jni_interface,
@@ -1293,8 +1293,8 @@ pub const Parser = struct {
         };
     }
 
-    const ForeignClassPrefix = struct {
-        runtime: ast.ForeignRuntime,
+    const RuntimeClassPrefix = struct {
+        runtime: ast.RuntimeKind,
         is_foreign: bool,
         is_main: bool,
     };
@@ -1305,7 +1305,7 @@ pub const Parser = struct {
     /// directive (possibly after modifiers). Consumes the modifier tokens
     /// only when a runtime directive follows; otherwise leaves the parser
     /// state untouched.
-    fn tryParseForeignClassPrefix(self: *Parser) ?ForeignClassPrefix {
+    fn tryParseForeignClassPrefix(self: *Parser) ?RuntimeClassPrefix {
         // Peek ahead through modifier tokens to confirm a directive follows.
         var lookahead_idx: usize = 0;
         var is_foreign = false;
@@ -1349,7 +1349,7 @@ pub const Parser = struct {
         return self.peekTag(1) == .identifier and self.peekTag(2) == .r_paren;
     }
 
-    fn foreignRuntimeForOffset(self: *Parser, offset: usize) ?ast.ForeignRuntime {
+    fn foreignRuntimeForOffset(self: *Parser, offset: usize) ?ast.RuntimeKind {
         const tag = self.peekTag(offset);
         return switch (tag) {
             .hash_jni_class => .jni_class,
@@ -1363,7 +1363,7 @@ pub const Parser = struct {
         };
     }
 
-    fn parseForeignClassDecl(self: *Parser, name: []const u8, start_pos: u32, runtime: ast.ForeignRuntime, is_foreign: bool, is_main: bool, name_is_raw: bool) anyerror!*Node {
+    fn parseForeignClassDecl(self: *Parser, name: []const u8, start_pos: u32, runtime: ast.RuntimeKind, is_foreign: bool, is_main: bool, name_is_raw: bool) anyerror!*Node {
         self.advance(); // skip directive token
 
         try self.expect(.l_paren);
@@ -1399,7 +1399,7 @@ pub const Parser = struct {
 
         try self.expect(.l_brace);
 
-        var members = std.ArrayList(ast.ForeignClassMember).empty;
+        var members = std.ArrayList(ast.RuntimeClassMember).empty;
         while (self.current.tag != .r_brace and self.current.tag != .eof) {
             // #extends Alias;  or  #implements Alias;
             if (self.current.tag == .hash_extends or self.current.tag == .hash_implements) {