Memory leak when opening files due to `max_width = 0.3` change

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Hi, I encountered a memory leak related to the recent change in commit [`5e0804e`](https://github.com/j-hui/fidget.nvim/commit/5e0804e7fb9511d046e52146f47f571278eabc33), where `max_width` was updated to `0.3`.

## Steps to reproduce
1. In a typescript project using the `vtsls` LSP, create a file named `required-permissions.decorator.ts`.
2. Open the file.
3. Observe excessive memory consumption, eventually leading to a memory leak.

## Workaround
Manually setting `max_width = 0` in the config prevents the issue:

```lua
{
"j-hui/fidget.nvim",
opts = {
notification = {
window = {
max_width = 0, -- `0` means no maximum width.
},
},
},
},

Start by reviewing commit 5e0804e and the notification window handling for max_width. Reproduce the leak in a TypeScript project with vtsls by opening required-permissions.decorator.ts, then compare behavior with max_width set to 0. Done means the default setting no longer causes excessive memory consumption while opening the file.

Written by the indexing model from the issue text.