refactor(chat): route browser chat through one runtime (P3 Slice-Zero Task 5) (#1172)

Co-authored-by: shaggy <[email protected]>

apps/web/src/spa/chat/use-harness-selection.ts

@@ -42,10 +42,6 @@ export interface HarnessSelectionValue {
    * resolves the composite option identity to the real entry and passes both
    * ids, so a bare model id is never combined with ambient provider state. */
   selectModel: (providerId: string, modelId: string) => void;
-  /** The compatibility `{provider, modelId}` projection for the legacy socket
-   * send path — derived ONLY from the validated persisted tuple, never from any
-   * free-text or unpersisted draft. Empty when nothing is sendable. */
-  projection: { provider?: string; modelId?: string };
 }
 
 /** A tuple is a currently-usable catalog option only when the catalog holds a
@@ -193,9 +189,6 @@ export function useHarnessSelection(): HarnessSelectionValue {
     !catalogUnavailable &&
     tuplesEqual(draft, persistedSelection) &&
     isAvailableInCatalog(persistedSelection, catalog);
-  const projection: { provider?: string; modelId?: string } = canSend
-    ? { provider: persistedSelection.providerId, modelId: persistedSelection.modelId }
-    : {};
 
   return {
     harnesses,
@@ -211,6 +204,5 @@ export function useHarnessSelection(): HarnessSelectionValue {
     selectHarness,
     selectProvider,
     selectModel,
-    projection,
   };
 }