Improvement (combobox): respect minimum popover width when trigger is narrow (#397)

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("Bug Fix", "Feature", "Documentation", "Maintenance", "Hotfix", "Improvement")
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## Description
When a `RubyUI::Combobox` trigger is narrower than the popover's natural content (e.g. a short trigger label like "Status"), the popover shrinks to match the trigger width and cuts off the `ComboboxSearchInput` placeholder.

`updatePopoverWidth` currently sets `popover.style.width = trigger.offsetWidth + "px"` unconditionally, coupling the popover's width to the trigger's width 1:1. The popover content has its own natural minimum that's independent of the trigger.

This PR introduces a `minPopoverWidth` Stimulus value (default `240`) and applies it as a floor inside `updatePopoverWidth`

The change is **monotonic**: it only expands popovers that would otherwise be narrower than the floor. Triggers wider than 240px are unaffected (no regression). `resize@window` already calls `updatePopoverWidth`, so the floor holds after viewport changes without any new event listeners.

Consumers can override the floor per-instance via the standard Stimulus values API:

```ruby
render RubyUI::Combobox.new(data: { "ruby-ui--combobox-min-popover-width-value": 320 })
  ...
end 
```


Before                     |  After
:-------------------------:|:-------------------------:
<img width="393" height="326" alt="Captura de Tela 2026-05-21 às 16 51 13" src="https://github.com/user-attachments/assets/9e618d90-dadc-4921-b65f-e96063ef81fd" />
   |  <img width="567" height="311" alt="Captura de Tela 2026-05-21 às 16 56 50" src="https://github.com/user-attachments/assets/f95e5803-ea1e-4807-9889-73e5cd461d59" />

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Prevents `RubyUI::Combobox` popovers from shrinking below a sensible width when the trigger is narrow, avoiding cut-off placeholders and cramped content.

- **Bug Fixes**
  - Added `minPopoverWidth` Stimulus value (default 240) and apply it as a floor in `updatePopoverWidth`.
  - Popover width is now `max(trigger width, minPopoverWidth)` and still updates on window resize.
  - Per-instance overrides supported via `ruby-ui--combobox-min-popover-width-value`.

<sup>Written for commit cf1310d. Summary will update on new commits. <a href="https://cubic.dev/pr/ruby-ui/ruby_ui/pull/397?utm_source=github">Review in cubic</a></sup>

<!-- End of auto-generated description by cubic. -->

Author: karinevieira

gem/lib/ruby_ui/combobox/combobox_controller.js

@@ -4,7 +4,8 @@ import { computePosition, autoUpdate, offset, flip } from "@floating-ui/dom";
 // Connects to data-controller="ruby-ui--combobox"
 export default class extends Controller {
   static values = {
-    term: String
+    term: String,
+    minPopoverWidth: { type: Number, default: 240 }
   }
 
   static targets = [
@@ -186,6 +187,7 @@ export default class extends Controller {
   }
 
   updatePopoverWidth() {
-    this.popoverTarget.style.width = `${this.triggerTarget.offsetWidth}px`
+    const width = Math.max(this.triggerTarget.offsetWidth, this.minPopoverWidthValue)
+    this.popoverTarget.style.width = `${width}px`
   }
 }