fix(frontend/new): make Scope textarea full width for better usability (#1189)

## Summary

Fix the layout of the Scope textarea on the publish settings (`/new`)
page.
Added `w-full` in `new.tsx` so the textarea now expands to the full
container width.

## Description

- Problem: On `/new` (publish settings), the Scope textarea renders too
narrow, which makes typing/reading awkward on typical viewports.
- Fix: Apply width: 100% (scoped to the publish form) so the control
uses the available space.
- Why safe: The selector is limited to the publish page; no other forms
are affected.
- Manual test: Run deno task prod:frontend, open http://jsr.test/new,
verify the Scope textarea spans the container width; check responsive
breakpoints.
- Screen shot
  - Before: 
- <img width="1364" height="594" alt="jsr_narrow_typing_spaxe"
src="https://github.com/user-attachments/assets/670a65a6-4fcd-4817-aac7-7a7c87bbe18d"
/>
  - After: 
- <img width="1351" height="587" alt="jsr_narrow_typing_spaxe_fixed"
src="https://github.com/user-attachments/assets/847cae5f-6417-4259-accd-75d27c7cb923"
/>
- <img width="480" height="504"
alt="jsr_narrow_typing_spaxe_fixed_mobile"
src="https://github.com/user-attachments/assets/d7e992e2-bd77-454f-8b03-975fa8e4fdc2"
/>


### PR Checklist

- [x] The PR title follows
[conventional commits](https://www.conventionalcommits.org/en/v1.0.0/)
- [ ] Is this closing an open issue? If so, link it, else include a
proper
      description of the changes and rason behind them.
- [x] Does the PR have changes to the frontend? If so, include
screenshots or a
      recording of the changes.
<br/>If it affect colors, please include screenshots/recording in both
      light and dark mode.
- [ ] Does the PR have changes to the backend? If so, make sure tests
are added.
<br/>And if changing dababase queries, be sure you have ran `sqlx
prepare`
      and committed the changes in the `.sqlx` directory.

Co-authored-by: Leo Kettmeir <[email protected]>

Author: nyaomaru

frontend/islands/new.tsx

@@ -228,7 +228,7 @@ function CreateScope(
         </label>
         <label class="flex items-center w-full md:w-full input-container pl-4 py-[2px] pr-[2px]">
           <textarea
-            class="input py-1.5 pr-4 pl-[1px] flex-grow-1 rounded-md"
+            class="input py-1.5 pr-4 w-full pl-[1px] flex-grow-1 rounded-md"
             name="description"
             placeholder="Enter a description for the scope (optional)"
             disabled={props.locked}