Route members by provider and model

[gitcommit90]

Maintainer change

Routes now select a provider family and model, while eligible accounts are tried internally before the next route member. Existing standard-provider route members migrate automatically; custom OpenAI-compatible endpoints remain connection-specific.

Verification

• npm test (310 passing)
• git diff --check
• Deterministic Electron route-editor capture, including picker reset behavior

Release notes

• Routes now select Provider, then Model instead of exposing individual accounts. ReRouted tries all eligible accounts for that provider/model before advancing to the next fallback or round-robin member.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.