fix: address delivery dedupe review follow-ups (#44666)

Merged via squash.

Prepared head SHA: 8e6d254cc4
Co-authored-by: frankekn <4488090+frankekn@users.noreply.github.com>
Co-authored-by: frankekn <4488090+frankekn@users.noreply.github.com>
Reviewed-by: @frankekn

src/gateway/server-methods/send.test.ts

@@ -334,6 +334,7 @@ describe("gateway send mirroring", () => {
           sessionKey: "agent:main:main",
           text: "caption",
           mediaUrls: ["https://example.com/files/report.pdf?sig=1"],
+          idempotencyKey: "idem-2",
         }),
       }),
     );

src/gateway/server-methods/send.ts

@@ -268,6 +268,7 @@ export const sendHandlers: GatewayRequestHandlers = {
                 agentId: effectiveAgentId,
                 text: mirrorText || message,
                 mediaUrls: mirrorMediaUrls.length > 0 ? mirrorMediaUrls : undefined,
+                idempotencyKey: idem,
               }
             : derivedRoute
               ? {
@@ -275,6 +276,7 @@ export const sendHandlers: GatewayRequestHandlers = {
                   agentId: effectiveAgentId,
                   text: mirrorText || message,
                   mediaUrls: mirrorMediaUrls.length > 0 ? mirrorMediaUrls : undefined,
+                  idempotencyKey: idem,
                 }
               : undefined,
         });