fix(providers): resolve the Codex auto-ping model from the live catalog instead of a retired id (#12361)

The opt-in Codex quota auto-ping pinned gpt-5.1-codex-mini. OpenAI shut that model down on 2026-07-23 and the repo's own lifecycle registry already rejects it on the request path, but the scheduler never consulted that gate — every window slide sent a dead id, hit the 15-minute failure cooldown, and retried the same id forever. The ping model now resolves per tick from the provider catalog through isModelSelectable(), the same gate chatCore uses, with the registry import kept lazy because this module sits on the instrumentation boot path (#12074). When nothing is selectable the provider is paused before any throttle slot, usage read or executor call, with one warning per state change.

Validated in a combined worktree with all 25 PRs of this batch boarded together: typecheck:core clean, 443/443 node-runner tests plus 14/14 vitest across every test file the batch touches, and check-changelog-integrity, check:cycles (418 files), check:provider-consistency (272 REGISTRY entries, 355 canonical providers), check:docs-counts, check:docs-sync (42 locales) and check-file-size all green.

Thanks @pacocartones.