feat: Add focusable option to Box

[eitanalka]

Issue

Summary

Add a focusable option to Box so it can be made focusable (default false). This enables the existing focusedBorderColor feature to actually work.

Motivation

Currently, Box has a focusedBorderColor option but Box cannot be focused, making this option useless. Adding focusable allows users to opt-in to focus behavior.

Proposed Changes

1. Add focusable setter to Renderable for dynamic prop updates
2. Add focusable option to BoxOptions (default false)
3. Add focused prop to BoxProps (React/Solid) for controlled focus state

Usage

// Imperative
const box = new Box({ focusable: true, focusedBorderColor: "blue", border: true })

// React/Solid JSX
<Box focusable focusedBorderColor="blue" border />
<Box focusable focused={isFocused} focusedBorderColor="blue" border />

Behavior

Usage	Result
new Box({})	Not focusable (default)
new Box({ focusable: true })	Focusable
new Box({ focusable: true, focusedBorderColor: "blue" })	Shows blue border when focused
<Box focusable />	Focusable via JSX boolean shorthand
<Box focusable focused={signal()} />	Controlled focus state

[pkg-pr-new]

@opentui/core

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core@585

@opentui/react

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/react@585

@opentui/solid

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@opentui/core-darwin-arm64

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@opentui/core-darwin-x64

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@opentui/core-linux-arm64

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@opentui/core-linux-x64

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@opentui/core-win32-arm64

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@opentui/core-win32-x64

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commit: ea12e68

[kommander]

@eitanalka I can't push to your branch, so you would have to run bun prettier:write in the repo to fix it. There should probably be a workflow to run fix & commit for PRs.

[eitanalka]

@kommander I updated the branch