Take the connector set as input to @corbits/connections

[TheGreatAxios]

Resolves CL-7384

Moves Workbench's concrete connector set (GitHub, Gmail, HuggingFace, OpenRouter, the eight non-OAuth inference providers, Granola/Manus/Exa/ScrapeCreators/Linear, and the curated MCP presets) out of @corbits/connections and into templates/connectors.ts — the product-data package. @corbits/connections now exports only the ConnectorDescriptor/ConnectorRegistry type shape, createConnectorRegistry, and route factories that take a registry/presets dependency (previously an optional test-only override defaulting to a baked-in constant); every route factory now requires it explicitly, with no fallback. The hub and web app pass templates/connectors.ts's CONNECTOR_REGISTRY/MCP_PRESETS in.

Also un-does an existing reverse dependency (@corbits/connections importing @workbench/templates/settings for the GitHub repo-review settings patch) by moving that generic arktype schema into @corbits/connections/template-settings, re-exported from templates/settings.ts for backward compatibility — needed so templates could take a real (not dev-only) dependency on @corbits/connections without a cycle.

MissingCredentialError now takes an optional displayName instead of looking one up in a registry it no longer carries.

Updated docs/connect-cards.md, docs/credential-wiring.md, packages/connections/README.md, and packages/plugins-ui/README.md to point at the new location.