Add debounce or optimization in symbol search

## Issue

Theres lag when i type anything in "Search for symbol" input

<img width="859" height="229" alt="Image" src="https://github.com/user-attachments/assets/29139a78-a186-40aa-87e3-2787ea0fed7a" />


## Reproduce

1. Click "Doc" tab that package has large symbols (ex. https://jsr.io/@fedify/vocab/doc)
2. Type anything in "Search for symbol" input"