refactor(ffi-linkage): Phase 9.3 — purge remaining 'foreign' from library/docs/example comments

Capital-Foreign + stale-identifier comment refs: library (Foreign Java types→Runtime,
foreign-class→runtime-class, foreign_class_map→runtime_class_map); docs/debugger
(foreign call→extern call); docs/fork-c ledger (foreign_class_map, protocol/foreign→
runtime-class); docs/inline-asm-design Deviation-6 obsolete #foreign-vs-extern design
RESOLVED to the landed extern/export reality; example comments (parseForeignClassDecl→
parseRuntimeClassDecl, checkForeignRefs→checkExternRefs, Foreign decls→Extern). Docs/
comments only — no build impact.

examples/0415-protocols-protocols.sx

@@ -193,9 +193,9 @@ sm_first :: (a: i32, b: i32) -> (i32, !) {
     return v;
 }
 
-// --- Foreign function binding ---
+// --- Extern function binding ---
 
-// --- Foreign function binding ---
+// --- Extern function binding ---
 libc :: #library "c";
 
 c_abs :: (n: i32) -> i32 extern libc "abs";

examples/1219-ffi-foreign.sx

@@ -14,7 +14,7 @@ c_abs :: (n: i32) -> i32 extern libc "abs";
 main :: () {
 
     // ========================================================
-    // 15. FOREIGN FUNCTION BINDING
+    // 15. EXTERN FUNCTION BINDING
     // ========================================================
     print("=== 15. Extern ===\n");
 

examples/1220-ffi-c-import-reserved-name-params.sx

@@ -1,5 +1,5 @@
 // `#import c` extern-name exemption: C names that collide with sx's reserved
-// type spellings import unedited. Foreign decls are treated as RAW — their names
+// type spellings import unedited. Extern decls are treated as RAW — their names
 // are never type-classified nor reserved-checked — so the generated `extern`
 // bindings import and call without hand-edits (no backticks needed). This covers
 // parameter names (`i1`/`i2`), a function whose own NAME is a reserved spelling

examples/1221-ffi-cstring-returns.sx

@@ -1,4 +1,4 @@
-// Foreign `-> [:0]u8` / `-> ?[:0]u8` returns: C hands back ONE `char *`;
+// Extern `-> [:0]u8` / `-> ?[:0]u8` returns: C hands back ONE `char *`;
 // the fat sx string is synthesized at the call boundary ({ptr, strlen};
 // NULL maps to the optional's null / an empty string) — issue 0128.
 // Pre-fix, the call read the pointer register pair as {ptr, len} and the

examples/1231-ffi-extern-undeclared-lib.sx

@@ -4,7 +4,7 @@
 // diagnostic — the bogus library reference is caught BEFORE the symbol
 // would silently resolve through whatever image happens to carry it.
 //
-// Regression (FFI-linkage Part B): `checkForeignRefs` validated only a
+// Regression (FFI-linkage Part B): `checkExternRefs` validated only a
 // `extern` (extern-import shape) library_ref and skipped the `extern` keyword's
 // `extern_lib`, so a bogus `extern` lib reference compiled silently (the
 // symbol resolved via the default image and ran). Prerequisite for

examples/1307-ffi-objc-expression-bodied-objc-method.sx

@@ -1,7 +1,7 @@
 // M1.0 (xfail) — '=>' expression-body form inside '#objc_class'
 // member methods.
 //
-// Today: parseForeignClassDecl ([src/parser.zig:1262]) accepts ';'
+// Today: parseRuntimeClassDecl ([src/parser.zig:1262]) accepts ';'
 // (declaration) or '{ ... }' (block body) but not '=>'. Trying
 // '=>' surfaces 'expected ;' at the arrow.
 //

examples/1318-ffi-objc-property-foreign.sx

@@ -30,7 +30,7 @@ probe_set_tag :: (self: *void, _cmd: *void, v: i32) callconv(.c) {
     g_probe_tag = v;
 }
 
-// Foreign declaration with #property on `tag`.
+// Extern declaration with #property on `tag`.
 SxPropProbe :: #objc_class("SxPropProbe") extern {
     alloc :: () -> *SxPropProbe;
     init  :: (self: *SxPropProbe) -> *SxPropProbe;

examples/1320-ffi-objc-extends-chain.sx

@@ -1,4 +1,4 @@
-// M2.3 — `#extends ForeignClass` method-resolution chaining.
+// M2.3 — `#extends a runtime class` method-resolution chaining.
 //
 // When `obj.method()` is called on a runtime-class pointer and
 // `method` isn't declared directly on the receiver's class, the