fix: support alpha-enabled multi-color filament hex values

[nozzle-1]

🎯 Description

Fixes a bug in filament entity picture generation when Spoolman returns multi-color hex values with an alpha channel, for example FF6A13FF.

Previously, multi-color values were only handled correctly when each hex color was 6 characters long. As a result, some valid multi-color filaments could fail to render their entity picture correctly when 8-character hex values were present.

This change keeps the multi-color values intact so Home Assistant can generate the filament picture without rejecting alpha-enabled colors.

🔗 Related Issue

No related issue.

This change is needed because some Spoolman setups return 8-character hex colors for multi-color filaments, which caused broken image generation in the integration.

🎨 Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🧹 Code refactoring (no functional changes)
• ⚡ Performance improvement
• ✅ Test update
• 🔧 Configuration change
• 🎨 UI/UX improvement

🧪 Testing

• I have tested this code locally
• I have added/updated unit tests that prove my fix/feature works
• All existing tests pass locally
• I have tested this in Home Assistant

Test Environment

• Home Assistant version: 2026.2.3
• Python version: 3.13.3
• Integration version: 1.24.0
• Spoolman version: 0.23.1

Test Scenarios

1. Configure a filament with multi_color_hexes containing standard 6-character values.
2. Configure a filament with multi_color_hexes containing 8-character values with alpha, such as FF6A13FF.
3. Confirm that the filament entity picture is generated correctly in both cases and no error is raised.

📸 Screenshots/Videos

Not applicable.

✅ Checklist

• 📖 My code follows the project's coding style
• 🔍 I have performed a self-review of my code
• 💬 I have commented my code, particularly in hard-to-understand areas
• 📚 I have updated the documentation (README, CONTRIBUTING, etc.) if needed
• ⚠️ My changes generate no new warnings or errors
• 🧪 I have added tests that prove my fix is effective or that my feature works
• ✅ New and existing unit tests pass locally with my changes
• 🌿 I am merging into the dev branch (not main)
• 📝 My commits follow the Conventional Commits specification
• 🔄 I have updated the integration version in manifest.json if needed
• 🌍 I have updated translations if I changed user-facing strings

📋 Commit Message Format

Example commit message used for this change:

• fix: support alpha-enabled multi-color filament hex values

🚀 Migration Notes

Not applicable.

📝 Additional Notes

This is a focused bug fix and does not change the public configuration or entity model.

🙏 Acknowledgments

Thanks to the maintainers for reviewing.

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