refactor: route TransportFor by provider name (#25650)

Delegate `aibridge` routing responsibility to the in-memory transport
layer.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

coderd/aibridge/factory.go

@@ -3,8 +3,6 @@ package aibridge
 import (
 	"context"
 	"net/http"
-
-	"github.com/google/uuid"
 )
 
 // Source identifies the call site that asked aibridge for a transport. It is
@@ -53,14 +51,20 @@ func DelegatedAPIKeyIDFromContext(ctx context.Context) (string, bool) {
 }
 
 // TransportFactory returns an [http.RoundTripper] that dispatches an aibridge
-// request in-process for a given ai_providers row.
+// request in-process for a given provider instance name.
 //
 // Implementations live in coderd/aibridged. coderd registers an in-process
 // factory on coderd.API.AIBridgeTransportFactory at startup so callers route
 // traffic through the daemon without going through the gated HTTP route.
 //
+// The returned RoundTripper is responsible for adapting the caller's request
+// to the aibridge daemon's mount path: callers hand it an upstream-shaped
+// request and the transport rewrites URL.Path to "/api/v2/aibridge/<name>/..."
+// before dispatching. Routing keys on the provider's instance name so callers
+// can use the same string the proxy daemon and the bridge mount use.
+//
 // Source is informational: implementations must not gate on it. It is attached
 // to the request context so handlers can include it in logs and metrics.
 type TransportFactory interface {
-	TransportFor(providerID uuid.UUID, source Source) (http.RoundTripper, error)
+	TransportFor(providerName string, source Source) (http.RoundTripper, error)
 }