Merge lang/foundations (9391695) into lang/editortools: no conflicts, selfhost/ identical to lang/foundations (the seeds unchanged; bootstrap-cfree fixpoint holds at 289532 lines), the help lists R10's --stdin-file, R8's syntax and R9's fmt / remove lines together

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/ludic-cli/test.ludic

@@ -1518,6 +1518,8 @@ function cmd_dev_test() -> int {
   smoke("library/cursor_capture")                    # #89 Input.cursor_mode compiles (no-op headless; windowed links cocoa.ll)
   smoke("rendering/gl_triangle")                     # Gl.* (OpenGL 4.1 core) compiles headless; the run needs a GPU context
 
+  syntax_cases()
+
   print("== the compiler and the CLI (ludicc / ludic) ==")
   # ludicc comes out of the IR seed with clang alone; the CLI is then compiled
   # by it, from Ludic.