Bug: Side notes cause infinite uvicorn reload loop

**Bug: Side notes cause infinite uvicorn reload loop**

**Symptom**: When a blog post `.ipynb` contains markdown footnotes (`[^1]` / `[^1]: ...` syntax), the dev server enters an infinite reload loop — uvicorn keeps detecting the post file as changed, restarts, detects it again, restarts again, endlessly. The page never finishes loading.

**Actual**: Server log shows repeated WatchFiles detections:

```
WARNING: WatchFiles detected changes in 'public/posts/xxx.ipynb'. Reloading...
INFO: Shutting down ... Started server process [N]
WARNING: WatchFiles detected changes in 'public/posts/xxx.ipynb'. Reloading...
... (infinite loop)
```

**What was tested**:
- I swapped the libraries on the same project — tried my PR branch, my latest full-featured branch, and the official code branch
- None of them worked — all three have the same infinite loop
- Posts without footnotes render correctly with no loop — the loop is specifically triggered by footnote syntax

The mentioned entry point is the uvicorn development server; reproduce with a post under public/posts/xxx.ipynb containing [^1] and [^1]: ... and compare it with a post without footnotes. Trace the WatchFiles detections and confirm done when the footnote post no longer triggers repeated reloads and finishes loading.

Written by the indexing model from the issue text.