Adds an opt-in `disabled_providers` config field plus the `shared/disabled-providers`
helper (`isProviderDisabled`, `filterDisabledProviderModels`, `applyDisabledProviders`)
that the plugin-config layer applies to resolved providers.
The routing changes in team-mode (team-runtime, tools/lifecycle, plugin/tool-registry)
are NOT in this PR — those are entangled with the `MemberSelectionMode` /
`ShutdownActor` refactors from the closed PR #3871 and need their own extraction
once those refactors land independently. This PR isolates the parts that are
cleanly independent: schema, helper, and config-layer wiring.
Companion to #4024 (live-tail tailer), both extracted from the closed PR #3871.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
PeterPonyu