compose_pills: Fix long text overflow in DM recipient box.

[adnan-td]

Removes the fixed height of the input field in compose DM recipient box. This commit makes the behaviour of recipient compose box equivalent to input pills used else where.

Fixes: #27688.

Screenshots and screen captures:

Before:

After:

Self-review checklist

• Self-reviewed the changes for clarity and maintainability
  (variable names, code reuse, readability, etc.).

Communicate decisions, questions, and potential concerns.

• Explains differences from previous plans (e.g., issue description).
• Highlights technical choices and bugs encountered.
• Calls out remaining decisions and concerns.
• Automated tests verify logic where appropriate.

Individual commits are ready for review (see commit discipline).

• Each commit is a coherent idea.
• Commit message(s) explain reasoning and motivation for changes.

Completed manual review and testing of the following:

• Visual appearance of the changes.
• Responsiveness and internationalization.
• Strings and tooltips.
• End-to-end functionality of buttons, interactions and flows.
• Corner cases, error conditions, and easily imagined bugs.

[adnan-td]

If still necessary, we can also implement character limit for the input field which would apply generally for all input_pills. Best way to do this would be to add a field on realm for storing the character limit for this use case and then cut off pasted text as already done in #29210.

[alya]

I guess in theory the character limit should match the character limit for the pill. So we'd potentially have a different character limit for users vs. streams, etc. It seems OK to take the max of all the values if it's easier not to customize it for different pill types.

[alya]

The screenshots look like an improvement to me!

[adnan-td]

It seems OK to take the max of all the values if it's easier not to customize it for different pill types.

One more thing I noticed is that pasting , separated long strings should still be allowed.
Tried implementing the character limit but not sure what to do in the above case.

[sujalshah-bit]

I manually tested it and everything looks good to me. One thing I noticed is that when you paste the text, the pasted text shakes a little bit. Although jitter is not related to this PR.

[adnan-td]

One thing I noticed is that when you paste the text, the pasted text shakes a little bit.

This happens due to pasting tries to pillify the pasted text. If the pasted text is valid, it forms pills without shaking.

[alya]

One more thing I noticed is that pasting , separated long strings should still be allowed.

Good point! Might not be worth worrying about a character limit, then.

[alya]

@adnan-td Can you please ping your mentor for review?

[adnan-td]

@Ujjawal3 @shubham-padia can you please review this.

[Ujjawal3]

I have looked at the code changes and looks good to me.

[alya]

Thanks! @karlstolley any feedback on this one, or is it ready for integration review?

[karlstolley]

Great! We're ready for integration review on this; I just tested and this works well with 16/140, so that height: 20px value was going to need to go anyway. Thanks, @adnan-td!

[timabbott]

Merged, thanks @adnan-td, @Ujjawal3 and @karlstolley!