fix(textinput): resolve placeholder truncation on initial render

[sebastianhuus]

Summary

• Fixes placeholder text being truncated to first character on initial render
• Resolves issue where placeholder displays correctly only after width is calculated

Problem

The placeholderView function in textinput.go was creating a rune slice with size m.Width+1. When m.Width is 0 during initial render, this created a slice of length 1, truncating multi-character placeholders to just their first character.

Solution

• Changed slice allocation from m.Width+1 to max(len(m.Placeholder), m.Width+1) to ensure it can always hold the full placeholder
• Updated early return condition to check len(m.Placeholder) instead of len(p)

Test plan

• Verified fix resolves the truncation issue with gum input commands
• Tested with long placeholder: "Enter your full name and email address here"
• Tested with medium placeholder: "Your message here"
• Tested with short placeholder: "Name"
• Confirmed existing functionality remains intact

All tests show full placeholder text immediately on render, no more truncation.

Fixes #779

[sebastianhuus]

I also tested some various length placeholders. They all rendered properly with the caret highlighted on the first character and allowing input without a duplicate placeholder line.

Pre fix behavior:

Post fix behavior:

[kwlzn]

@sebastianhuus @meowgorithm can we get this landed?

[sebastianhuus]

@kwlzn currently ill but I can take a look during the week and update my fork.

While looking at other similar PRs and their Discord, I got the impression that changes like this weren't prioritized because they're working on shipping v2 of bubbles. I haven't followed the space since then so I'm not sure if that's still a concern. From what I understood V2 contains extra terminal-specific features and support for a lot more terminals.

[sebastianhuus]

@kwlzn I see #768 (merged October 2025) includes a refactor that also addresses this bug. It was shipped to v2.0.0-rc.1 (November 2025), but Gum uses Bubbles v0.21 (April 2025).

@meowgorithm If you could ship this fix before v2, then I suggest to release a intermediary patch v0.21.1 or v0.22 is released for Bubbles and Gum's dependency is updated respectively.

I tested Master branch of Bubbles as dependency for gum and the bug is fixed for me.

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