refactor(ffi-linkage): Phase 9.3 — rename *-foreign* example files → extern/runtime names

git-mv the 10 foreign-named example families to extern/runtime-class names + update
every #import/#include/#source ref, stale comment ref, and the 1172 stderr snapshot
(path + 'extern symbol' message). Renames: 0729…-foreign→…-extern, 1172-diagnostics-
foreign-symbol-conflict→…-extern-symbol-conflict, 1205/1207 ffi-foreign-global→
ffi-extern-global, 1216/1217 ffi-…-foreign-(in-method|result-chain)→…-extern-…,
1219-ffi-foreign→1219-ffi-extern, 1306 objc-foreign-class-chained→objc-runtime-class-
chained, 1318 objc-property-foreign→objc-property-extern-class. DEDUP: deleted
1218-ffi-foreign-cvariadic (identical to 1229-ffi-extern-cvariadic; updated 1229's
twin ref) + the orphaned 1620 dir. Also purged editors/vscode tmLanguage (#foreign
dropped from the directive highlighter) + 1220.h/issues-0030.sx comment refs. Suite
green (644 corpus / 443 unit, 0 failed).

editors/vscode/syntaxes/sx.tmLanguage.json

@@ -179,7 +179,7 @@
       "patterns": [
         {
           "name": "keyword.other.directive.sx",
-          "match": "#(?:run|import|insert|builtin|foreign|library)\\b"
+          "match": "#(?:run|import|insert|builtin|library)\\b"
         }
       ]
     },

examples/0729-modules-flat-same-name-extern.sx

@@ -5,8 +5,8 @@
 // dispatch binds the call. A same-name extern collision therefore compiles and
 // runs (master behavior), it does NOT error as ambiguous.
 #import "modules/std.sx";
-#import "0729-modules-flat-same-name-foreign/a.sx";
-#import "0729-modules-flat-same-name-foreign/b.sx";
+#import "0729-modules-flat-same-name-extern/a.sx";
+#import "0729-modules-flat-same-name-extern/b.sx";
 
 main :: () -> i32 {
     print("absval = {}\n", absval(-7));

examples/1205-ffi-extern-global-helper.sx

@@ -1,4 +1,4 @@
-// Companion module for examples/94-foreign-global.sx (PLAN-FFI 0.10).
+// Companion module for examples/1205-ffi-extern-global.sx (PLAN-FFI 0.10).
 // Declares the same `extern` extern global as the main file; the
 // linker should treat both decls as one symbol. We deliberately don't
 // READ `@__stdinp` from inside a helper fn body — that path is busted

examples/1205-ffi-extern-global.sx

@@ -4,7 +4,7 @@
 // `<fn> :: (...) -> ... extern;` form on the function side.
 //
 // Cross-file dimension (PLAN-FFI step 0.10): the helper companion
-// `94-foreign-global-helper.sx` ALSO declares `__stdinp : *void extern;`.
+// `1205-ffi-extern-global-helper.sx` ALSO declares `__stdinp : *void extern;`.
 // Both files referencing the same extern symbol must link cleanly —
 // LLVM dedupes the named global, the C linker resolves both refs to
 // the one libSystem symbol.
@@ -15,7 +15,7 @@
 // the equality check here.
 
 #import "modules/std.sx";
-#import "1205-ffi-foreign-global-helper.sx";
+#import "1205-ffi-extern-global-helper.sx";
 
 __stdinp : *void extern;
 

examples/1216-ffi-08-extern-in-method.c

@@ -1,3 +1,3 @@
-#include "1216-ffi-08-foreign-in-method.h"
+#include "1216-ffi-08-extern-in-method.h"
 
 int ffi_method_helper(int x) { return x * 10; }

examples/1216-ffi-08-extern-in-method.sx

@@ -12,8 +12,8 @@
 #import "modules/build.sx";
 
 #import c {
-    #include "1216-ffi-08-foreign-in-method.h";
-    #source "1216-ffi-08-foreign-in-method.c";
+    #include "1216-ffi-08-extern-in-method.h";
+    #source "1216-ffi-08-extern-in-method.c";
 };
 
 // ── 1. Struct method calling a #extern fn ───────────────────────────

examples/1217-ffi-09-extern-result-chain.c

@@ -1,4 +1,4 @@
-#include "1217-ffi-09-foreign-result-chain.h"
+#include "1217-ffi-09-extern-result-chain.h"
 #include <stdlib.h>
 
 void *ffi_chain_make(int seed) {

examples/1217-ffi-09-extern-result-chain.sx

@@ -12,8 +12,8 @@
 #import "modules/std.sx";
 
 #import c {
-    #include "1217-ffi-09-foreign-result-chain.h";
-    #source "1217-ffi-09-foreign-result-chain.c";
+    #include "1217-ffi-09-extern-result-chain.h";
+    #source "1217-ffi-09-extern-result-chain.c";
 };
 
 // Struct field hosts an FFI-returned handle.

examples/1218-ffi-foreign-cvariadic.c

@@ -1,30 +0,0 @@
-#include <stdarg.h>
-
-long long sx_ffi_sum_ints(int n, ...) {
-    va_list ap;
-    va_start(ap, n);
-    long long total = 0;
-    for (int i = 0; i < n; i++) total += va_arg(ap, int);
-    va_end(ap);
-    return total;
-}
-
-double sx_ffi_avg_doubles(int n, ...) {
-    va_list ap;
-    va_start(ap, n);
-    double total = 0.0;
-    for (int i = 0; i < n; i++) total += va_arg(ap, double);
-    va_end(ap);
-    if (n == 0) return 0.0;
-    return total / n;
-}
-
-int sx_ffi_count_args(const char *tag, ...) {
-    (void) tag;
-    va_list ap;
-    va_start(ap, tag);
-    int count = 0;
-    while (va_arg(ap, const char *) != 0) count++;
-    va_end(ap);
-    return count;
-}

examples/1218-ffi-foreign-cvariadic.sx

@@ -1,28 +0,0 @@
-// `extern` C-variadic tail: trailing `..args: []T` on a extern fn maps
-// to the C calling convention's `...`. Extras at the call site are
-// passed via the variadic slot with the standard default argument
-// promotion (i8/i16/bool → i32, f32 → f64) applied implicitly.
-
-#import "modules/std.sx";
-
-#import c {
-    #source "1218-ffi-foreign-cvariadic.c";
-};
-
-sx_ffi_sum_ints     :: (n: i32, ..args: []i32) -> i64 extern;
-sx_ffi_avg_doubles  :: (n: i32, ..args: []f64) -> f64 extern;
-sx_ffi_count_args   :: (tag: *u8, ..args: []*u8) -> i32 extern;
-
-main :: () -> i32 {
-    print("sum_ints(3, 10, 20, 30) = {}\n", sx_ffi_sum_ints(3, 10, 20, 30));
-    print("sum_ints(0)             = {}\n", sx_ffi_sum_ints(0));
-    print("avg_doubles(2)          = {}\n", sx_ffi_avg_doubles(2, 1.5, 2.5));
-    print("avg_doubles(3)          = {}\n", sx_ffi_avg_doubles(3, 1.0, 2.0, 3.0));
-
-    a := "alpha".ptr;
-    b := "beta".ptr;
-    g := "gamma".ptr;
-    sentinel : *u8 = null;
-    print("count_args(3 strs)      = {}\n", sx_ffi_count_args("tag".ptr, a, b, g, sentinel));
-    0
-}

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

@@ -1,6 +1,6 @@
-/* Foreign C declarations whose names collide with sx's reserved type spellings.
+/* Extern C declarations whose names collide with sx's reserved type spellings.
    The `#import c` exemption must accept these generated names unedited, both as
-   parameter names (`i1`, `i2`) and as a FUNCTION name (`i2`) — and a foreign
+   parameter names (`i1`, `i2`) and as a FUNCTION name (`i2`) — and an extern
    reserved-name function must be bare-callable (issue 0089). */
 int ffi_pick(int i1, int i2, int which);
 int ffi_sum(int i1, int i2);

examples/1229-ffi-extern-cvariadic.sx

@@ -1,6 +1,5 @@
 // `extern` C-variadic tail: a trailing `..args: []T` on an `extern` fn
-// maps to the C calling convention's `...`, exactly like its `extern`
-// twin (example 1218). Extras at the call site pass through the variadic
+// maps to the C calling convention's `...`. Extras at the call site pass through the variadic
 // slot with standard default argument promotion (i8/i16/bool → i32,
 // f32 → f64), NOT packed into an sx slice.
 //

examples/1620-cimport-foreign-ref-unvalidated/ref.c

@@ -1 +0,0 @@
-int ref_answer(void) { return 7; }

examples/expected/1172-diagnostics-extern-symbol-conflict.stderr

@@ -1,5 +1,5 @@
 error: extern symbol 'getenv' is already bound with a different signature; two views of one C symbol must declare identical types
-  --> examples/1172-diagnostics-foreign-symbol-conflict.sx:9:61
+  --> examples/1172-diagnostics-extern-symbol-conflict.sx:9:61
    |
  9 | getenv_opt :: (name: [:0]u8) -> ?[:0]u8 extern libc "getenv";
    |                                                             ^

examples/expected/1218-ffi-foreign-cvariadic.stdout

@@ -1,5 +0,0 @@
-sum_ints(3, 10, 20, 30) = 60
-sum_ints(0)             = 0
-avg_doubles(2)          = 2.000000
-avg_doubles(3)          = 2.000000
-count_args(3 strs)      = 3

examples/expected/1318-ffi-objc-property-foreign.exit

@@ -1 +0,0 @@
-0

examples/expected/1318-ffi-objc-property-foreign.stderr

@@ -1 +0,0 @@
-

issues/0030-extern-global-declarations.sx

@@ -1,8 +1,8 @@
 // Repro for issue 0030 (OPEN feature request): cross-file sx `extern` globals.
 // Want: `extern G : T;` declares a reference to a global defined in another sx
-// file (resolved at link time), mirroring `#foreign` functions. Today this is a
-// parse error — the form doesn't exist. Distinct from `name : T #foreign;`
-// (an external C data symbol; see examples/1205-ffi-foreign-global.sx).
+// file (resolved at link time), mirroring `extern` functions. Today this is a
+// parse error — the form doesn't exist. Distinct from `name : T extern;`
+// (an external C data symbol; see examples/1205-ffi-extern-global.sx).
 //
 // Expected (once implemented): parses; `g_x` resolves to a global defined
 // elsewhere. Actual: error "expected '::', ':=', or ':' after identifier".