dx serve not watching sub-modules

**Problem**

I have a dioxus project with various modules in src, and then a sub-module for charting. Changes to source in the top-level files triggers `dx serve` to rebuild and launch the app. Changes to source in the nested folder does not.

**Expected behavior**

Changes to code in nested modules should trigger a rebuild and relaunch. It does not. Pressing `r` does a manual rebuild and relaunch, pulling in any changes in the nested module.

**Environment:**

- Dioxus version: 0.7.3 (22b06ba)
- Rust version: 1.96.0-nightly (80381278a 2026-03-01)
- OS info: Devuan excalibur
- App platform: linux

**Questionnaire**

I'm interested in fixing this myself but don't know where to start.

Start by reproducing the issue with `dx serve`: edit a top-level source file and then a source file in a nested module under `src`, and observe which changes trigger rebuilding. Trace the `dx serve` file-watching entry point and identify why nested module changes are missed. Done means edits anywhere in nested source modules trigger the same rebuild and relaunch as top-level edits.

Written by the indexing model from the issue text.