[Improve] Default GitHub Copilot roles to GPT 5.6 Luna

[roomote-community]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Make GPT 5.6 Luna the recommended GitHub Copilot coding model, with every other role following that model through the existing fallback behavior.
• Keep one explicit medium reasoning setting for Luna instead of persisting conflicting per-role settings against the same OpenCode model entry.
• Cover the complete resolved Copilot deployment preset in the provider configuration tests.

Why this change was made

GitHub Copilot subscriptions have a constrained usage allowance, and Luna provides a substantially cheaper default while remaining competitive across Roomote's role evaluations.

Impact

New or reapplied GitHub Copilot recommendations use Luna across every model role without collapsing multiple reasoning settings onto one provider model entry. Existing manually configured deployment models are unaffected until an operator applies the recommended provider preset.

[roomote-community]

No code issues found. See task

• packages/types/src/model-provider-config.ts:826 Shared Luna model collapses the configured role-specific reasoning levels at runtime.

_{Reviewed 876a0fa}