feat: add live character counter to command input

[jahnavipriya7]

Description

Added a real-time character counter to the command input bar.

Features

• Live character count updates while typing
• Displays current count against configurable limit
• Counter turns red when limit exceeds
• Minimal UI impact

Fixes #224

[jahnavipriya7]

Implemented the requested real-time character counter feature. Looking forward to feedback. Thanks!

[VyomKulshrestha]

Thanks for implementing the character counter!

We have a couple of suggestions for improvement:

1. Enforce the Limit: Currently, the counter turns red when the count exceeds 20,000, but the form is still allowed to submit and the submit button remains active. If 20,000 is a strict limit, either the submit button should be disabled when the limit is exceeded, or you should set maxlength="20000" on the <input> element.
2. Styling/Alignment: The .char-counter has margin-top: 4px; but is placed inside a horizontal flexbox container (.input-wrapper). This might cause vertical alignment misalignment inside the input bar. It would be cleaner to align it using standard flex utilities or position it relative to the input field.