break another cycle

packages/@ember/-internals/glimmer/lib/templates/input.ts

@@ -1,5 +1,5 @@
 import { precompileTemplate } from '@ember/template-compilation';
-import { on } from '@ember/modifier';
+import { on } from '@ember/modifier/on';
 export default precompileTemplate(
   `<input
   {{!-- for compatibility --}}

packages/@ember/-internals/glimmer/lib/templates/link-to.ts

@@ -1,5 +1,5 @@
 import { precompileTemplate } from '@ember/template-compilation';
-import { on } from '@ember/modifier';
+import { on } from '@ember/modifier/on';
 
 export default precompileTemplate(
   `<a

packages/@ember/-internals/glimmer/lib/templates/textarea.ts

@@ -1,5 +1,5 @@
 import { precompileTemplate } from '@ember/template-compilation';
-import { on } from '@ember/modifier';
+import { on } from '@ember/modifier/on';
 
 export default precompileTemplate(
   `<textarea

packages/@ember/modifier/index.ts

@@ -1,22 +1,9 @@
-import { on as glimmerOn } from '@glimmer/runtime';
 import { setModifierManager as glimmerSetModifierManager } from '@glimmer/manager';
 
-import type { Opaque } from '@ember/-internals/utility-types';
 import type Owner from '@ember/owner';
 import type { ModifierManager } from '@glimmer/interfaces';
 
-// In normal TypeScript, this modifier is essentially an opaque token that just
-// needs to be importable. Declaring it with a unique interface like this,
-// however, gives tools like Glint (that *do* have a richer notion of what it
-// is) a place to install more detailed type information.
-// eslint-disable-next-line @typescript-eslint/no-empty-interface
-export interface OnModifier extends Opaque<'modifier:on'> {}
-
-// SAFETY: at the time of writing, the cast here is from `{}` to `OnModifier`,
-// which makes it strictly safer to use outside this module because it is not
-// usable as "any non-null item", which is what `{}` means, without loss of any
-// information from the type itself.
-export const on = glimmerOn as OnModifier;
+export { on, type OnModifier } from './on';
 
 // NOTE: this uses assignment to *require* that the `glimmerSetModifierManager`
 // is legally assignable to this type, i.e. that variance is properly upheld.

packages/@ember/modifier/on.ts

@@ -0,0 +1,16 @@
+import { on as glimmerOn } from '@glimmer/runtime';
+
+import type { Opaque } from '@ember/-internals/utility-types';
+
+// In normal TypeScript, this modifier is essentially an opaque token that just
+// needs to be importable. Declaring it with a unique interface like this,
+// however, gives tools like Glint (that *do* have a richer notion of what it
+// is) a place to install more detailed type information.
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+export interface OnModifier extends Opaque<'modifier:on'> {}
+
+// SAFETY: at the time of writing, the cast here is from `{}` to `OnModifier`,
+// which makes it strictly safer to use outside this module because it is not
+// usable as "any non-null item", which is what `{}` means, without loss of any
+// information from the type itself.
+export const on = glimmerOn as OnModifier;

packages/@ember/modifier/package.json

@@ -3,7 +3,8 @@
   "private": true,
   "type": "module",
   "exports": {
-    ".": "./index.ts"
+    ".": "./index.ts",
+    "./on": "./on.ts"
   },
   "dependencies": {
     "@ember/-internals": "workspace:*",