update docs for compile chain

docs/c-modules.md

@@ -52,10 +52,13 @@ Where:
 Examples:
 - `mypackage/math.c` -> `js_mypackage_math_use`
 - `gitea.pockle.world/john/lib/render.c` -> `js_gitea_pockle_world_john_lib_render_use`
+- `mypackage/internal/helpers.c` -> `js_mypackage_internal_helpers_use`
 - `mypackage/game.ce` (AOT actor) -> `js_mypackage_game_program`
 
 Actor files (`.ce`) use the `_program` suffix instead of `_use`.
 
+Internal modules (in `internal/` subdirectories) follow the same convention — the `internal` directory name becomes part of the symbol. For example, `internal/os.c` in the core package has the symbol `js_core_internal_os_use`.
+
 **Note:** Having both a `.cm` and `.c` file with the same stem at the same scope is a build error.
 
 ## Required Headers