docs(cli): clarify shell command behavior

Author: aiirvizionz

src/commands.mjs

@@ -158,7 +158,7 @@ const COMMANDS = [
 
   {
     name: "shell",
-    summary: "run a shell command (blocking, spawnSync $SHELL -c)",
+    summary: "run a shell command (blocking, cmd.exe on Windows or $SHELL -c elsewhere)",
     // The moshscript system verb for arbitrary shell commands. Blocking
     // (spawnSync + inherited stdio) so it runs inline in the no-`await` style,
     // and the child owns the terminal for interactive commands. Returns

test/commands.test.mjs

@@ -83,3 +83,9 @@ test("the vocabulary exposes summaries for `moshcode commands`", () => {
     assert.ok(cmd.summary.length > 0, `${cmd.name}() needs a summary`);
   }
 });
+
+test("shell() summary describes the portable shell behavior", () => {
+  const cmd = moshVocabulary().get("shell");
+  assert.match(cmd.summary, /cmd\.exe on Windows/);
+  assert.match(cmd.summary, /\$SHELL -c elsewhere/);
+});