fix(copilot): expose only account-available models

[hgaol]

Title

fix(copilot): expose only account-available models

Description

Summary

GitHub Copilot model discovery could expose models the connected account could not use.

This fixes both sources:

1. Provider response filtering

   • Policy-free models remain valid.
   • A present policy must be exactly enabled.
   • disabled, unconfigured, unknown, and malformed policies are excluded.
   • Existing picker, tool-call, and supported-wire requirements remain unchanged.

2. Catalog persistence

   • Copilot's filtered /models response is treated as the account's authoritative usable catalog.
   • The first account-scoped discovery replaces bootstrap fallback IDs with the available account models.
   • Later refreshes remove withdrawn IDs while preserving still-available user selections.
   • Newly introduced models remain opt-in after the initial discovery.
   • If an unavailable default must be replaced, reconciliation selects an available model.

The generic reconciliation behavior for other providers is unchanged: their model lists may be partial, so omitted user-selected IDs remain preserved.

Fixes #4697

Root cause

toGitHubCopilotModelInfo rejected only:

policy?.state === 'disabled'

That admitted unconfigured models even though Maka cannot accept their policy terms.

Separately, reconcileConnectionAfterModelFetch intentionally preserved every previously enabled model. Interactive Copilot connections start with fallback IDs, so models absent from the account response were added back into the projected catalog.

Verification

The regressions fail without this change and pass with it:

• Provider-contract fixture with:
  • policy-free model;
  • enabled model;
  • disabled model;
  • unconfigured model;
  • hidden-picker model;
  • tool-incompatible model;
  • unsupported endpoint.
• Core authoritative-reconciliation tests:
  • initial fallback replacement;
  • withdrawn model removal;
  • still-available user choice preservation;
  • newly introduced model remains opt-in.
• Runtime Policy integration test proving unavailable bootstrap IDs are removed from persisted Copilot state.

Checks run:

• Provider conformance matrix: 126 passed
• @maka/core: 782 passed
• @maka/storage: 1107 tests, 0 failures
• @maka/runtime: 3176 tests, 0 failures
• Full workspace build: passed
• Full workspace typecheck: passed
• Lint: passed
• Format check: passed
• ASF source-header check: passed

The focused regressions and full typecheck/lint/format were rerun after merging the latest main.

AI use

Select exactly one:

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

Tool(s) and scope: pi with an OpenAI model assisted diagnosis, primary-source comparison against GitHub's Copilot client, implementation, test creation, and verification. The human contributor remains responsible for the change.

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 — GitHub Copilot model lists now omit models that are unavailable to the connected account.
• No