fix: restore composer alignment follow-up

[Just-Insane]

Description

Restore the upstream room composer wrapper alignment so the composer text baseline, placeholder, and inline emoji sit correctly again.

Related to #339

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).
  The AI-assisted portion restores the editor row's upstream vertical alignment in src/app/components/editor/Editor.tsx and removes the extra single-line bottom inset in src/app/components/editor/Editor.css.ts, which brings composer text and inline emoji back into the same visual position as Sable.

[github-actions]

Sentry Preview Error Triage

No Sentry errors found for this PR's preview deployment as of Tue, 23 Jun 2026 17:25:54 GMT.

This comment updates automatically after each push.

[github-code-quality]

Code Coverage Overview

Languages: JavaScript

JavaScript / code-coverage/vitest

The overall coverage remains at 27%, unchanged from the integration branch.

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[github-actions]

Deploying with    Cloudflare Workers

Status	Preview URL	Commit	Alias	Updated (UTC)
✅ Deployment successful!	https://pr-343-charm.justin-tech.workers.dev	71e27e4	pr-343	Tue, 23 Jun 2026 18:30:29 GMT