fix: composer input overflow with long unbroken strings

[shubhook]

Description

Fixed composer input overflow when typing or pasting long unbroken strings (no spaces).
The text was overflowing the input area causing layout shift and send button misalignment.

Added overflow-wrap: break-word and word-break: break-word to .tiptap class in
TipTapEditor.css, and min-width: 0 to the flex container in ContinueInputBox.tsx.

Fixes #13016

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Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created

Screen recording or screenshot

Before:

After:

Diff:

Tests

This is a CSS-only fix with no behavioral logic changes. No new tests were added as
the fix is purely visual and verified manually by reproducing the overflow with a
100+ character unbroken string before and after the change.

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[shubhook]

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