[FEATURE]: add melious.ai provider support

[kostadin-damyanov-prime]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

It would be nice if opencode supports API key and subscription plan from the https://melious.ai/ provider out of the box.

[github-actions]

This issue might be a duplicate of existing issues requesting support for new AI providers. Please check:

• [FEATURE]: Support new provider: Maple ( https://trymaple.ai ) #36789: [FEATURE]: Support new provider: Maple (trymaple.ai)
• [FEATURE]: Add OfoxAI as a supported AI provider #37327: [FEATURE]: Add OfoxAI as a supported AI provider
• [FEATURE]: Add Muse Spark / Muse Code as a provider #41551: [FEATURE]: Add Muse Spark / Muse Code as a provider
• [FEATURE]: Add Corvex as a provider (models.dev + providers docs) #45935: [FEATURE]: Add Corvex as a provider
• [FEATURE]: Please add native provider: unsloth-studio #46975: [FEATURE]: Please add native provider: unsloth-studio

If your request is distinct from these (e.g., melious.ai has unique capabilities or integration requirements not covered by existing provider requests), please clarify what makes it different.