ffi 2.7 xfail: other six type-introducer directive forms parse

#jni_interface, #objc_class, #objc_protocol, #swift_class,
#swift_struct, #swift_protocol — each with the same body grammar as
#jni_class. Today the lexer doesn't recognise any of these directives
and the parser errors at the first one (`#jni_interface`). The
make-green follow-up adds the six lexer tokens and refactors
`JniClassDecl` into `ForeignClassDecl` with a `runtime` discriminator
so all seven forms share one AST shape and one parser path.

examples/ffi-jni-class-07-all-runtimes.sx

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+// Phase 2 step 2.7 (PLAN-FFI.md): xfail then green for the remaining
+// six type-introducer directive forms parsing with the same body
+// grammar as `#jni_class`. No codegen yet — Phase 3 picks up Obj-C
+// codegen, Phase 4 picks up Swift.
+//
+// The directives this step turns on:
+//   #jni_interface  — Java interface binding
+//   #objc_class     — Obj-C class binding
+//   #objc_protocol  — Obj-C protocol binding
+//   #swift_class    — Swift class binding (via @_cdecl bridge)
+//   #swift_struct   — Swift @frozen value-type binding
+//   #swift_protocol — Swift @objc-bridgeable protocol binding
+//
+// Internally the AST collapses into one `foreign_class_decl` node
+// carrying a `runtime` discriminator. Today the parser rejects each
+// of these because the lexer doesn't recognise the directive name.
+
+#import "modules/std.sx";
+
+IFoo :: #jni_interface("com/example/IFoo") {
+    bar :: (self: *Self) -> s32;
+}
+
+NSString :: #objc_class("NSString") {
+    length :: (self: *Self) -> s32;
+}
+
+NSCopying :: #objc_protocol("NSCopying") {
+    copy :: (self: *Self) -> *Self;
+}
+
+URL :: #swift_class("Foundation.URL") {
+    absoluteString :: (self: *Self) -> *void;
+}
+
+Date :: #swift_struct("Foundation.Date") {
+    timeIntervalSince1970 :: (self: *Self) -> f64;
+}
+
+Hashable :: #swift_protocol("Swift.Hashable") {
+    hash :: (self: *Self) -> s32;
+}
+
+main :: () -> s32 {
+    print("parse-only ok\n");
+    0;
+}

tests/expected/ffi-jni-class-07-all-runtimes.exit

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+1

tests/expected/ffi-jni-class-07-all-runtimes.txt

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+/Users/agra/projects/sx/examples/ffi-jni-class-07-all-runtimes.sx:20:9: error: unexpected token in expression