[Cleanup] Group GatewayDispatcherDeps fields by concern

## What problem are you trying to solve?

The `GatewayDispatcherDeps` interface has grown to 31 fields. While each field is a real dependency, the flat list makes construction verbose and signals the dispatcher may be doing too much. Grouping by concern would improve readability and make it easier to identify future decomposition opportunities.

## Where

`packages/core/src/services/gateway-dispatcher.ts` — the `GatewayDispatcherDeps` interface (around lines 72-132).

## What needs to be done

1. Open `packages/core/src/services/gateway-dispatcher.ts`
2. Find the `GatewayDispatcherDeps` interface
3. Group the fields into sub-interfaces by concern. Suggested grouping:

```ts
interface StoreDeps {
getTaskStore: () => TaskStore;
getMessageStore: () => MessageStore;
getActiveTaskId: () => string | null;
markUnread: (taskId: string) => void;
}

interface GatewayStatusDeps {
setGatewayStatusByGateway: ...;
setGatewayVersion: ...;
setGatewayReconnectInfo: ...;
setDefaultGatewayId: ...;
setGatewayInfoMap: ...;
setGatewaysLoaded: ...;
getGatewayInfoMap: ...;
}

interface CatalogDeps {
setModelCatalogForGateway: ...;
setAgentCatalogForGateway: ...;
setToolsCatalogForGateway: ...;
setSkillsStatusForGateway: ...;
}
```

4. Compose the main interface: `interface GatewayDispatcherDeps extends StoreDeps, GatewayStatusDeps, CatalogDeps { ... remaining fields }`
5. Update the construction site(s) that build this deps object
6. Run `pnpm check` to verify nothing breaks

## Why does this matter?

A 31-field flat interface is hard to scan and construct. Grouping by concern makes dependencies self-documenting and eases future refactoring if the dispatcher is decomposed.

## Primary area

Task execution

Start in packages/core/src/services/gateway-dispatcher.ts at the GatewayDispatcherDeps interface around lines 72-132. Group its fields into concern-based sub-interfaces, compose the main interface, and locate the construction sites that build the dependency object. Run pnpm check; done means the dependencies are grouped without breaking type checking.

Written by the indexing model from the issue text.