Help Center: Display message inside input field until its sent

[agrullon95]

Fixes: https://github.com/Automattic/dotcom-forge/issues/9798

Proposed Changes

• Fix loading spinner styling when the attachment button is visible.
• Keep the chat message input field populated until the message is sent and appears in the chat container.

Why are these changes being made?

• The spinner is incorrectly displayed above the attachment button.
• Keep visibility of the user's message until its sent/displayed in the chat container.

Testing Instructions

• Checkout branch or use live link ( FLAG = flags=help-center-experience)
• Open the Help Center without the flag enabled, start a chat, send a message.
• Verify the loading spinner is in the correct location while the message is being sent
• Verify the message input field placeholder text says "Just a moment..." while the message is being sent.
• Enable the flag: flags=help-center-experience and open the Help Center again.
• Open an existing support chat, send a message, andverify the message persists in the input field (disabled state) until the chat container is populated.
• Open a new conversation (only AI chat) and verify the place holder message "Just a moment..." appears in the input field while sending a message.

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
  • For UI changes, have we tested the change in various languages (for example, ES, PT, FR, or DE)? The length of text and words vary significantly between languages.
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

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[matticbot]

Here is how your PR affects size of JS and CSS bundles shipped to the user's browser:

Async-loaded Components (~37 bytes added 📈 [gzipped])

name                               parsed_size           gzip_size
async-load-automattic-help-center       +241 B  (+0.0%)      +37 B  (+0.0%)

React components that are loaded lazily, when a certain part of UI is displayed for the first time.

Legend

What is parsed and gzip size?

Parsed Size: Uncompressed size of the JS and CSS files. This much code needs to be parsed and stored in memory.
Gzip Size: Compressed size of the JS and CSS files. This much data needs to be downloaded over network.

Generated by performance advisor bot at iscalypsofastyet.com.

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• help-center
• notifications
• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug update/disappearing-sent-message on your sandbox.