fix(copilot): hide unavailable and unconfigured models

[seekskyworld]

Summary

Fixes #4697

GitHub Copilot model discovery now treats the account /models response as authoritative: policy-free and enabled models remain visible, disabled and unconfigured models are excluded, and refreshes drop bootstrap fallback ids that are no longer in the live catalog without auto-selecting a replacement.

Verification

• npm exec -- tsx --test packages/runtime/src/__tests__/provider-contract-overrides.ts
• npm exec -- tsx --test packages/storage/src/__tests__/runtime-policy-model-facts.test.ts

AI use

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope:

• Codex: implemented the Copilot model fetch/filter fix, added regression tests, and updated the local coordination/history notes.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No