fix(ag-ui): accumulate streamed TOOL_CALL_ARGS deltas #1693

Job	Run time
CI scope	1m 53s
Cockpit — representative capability smoke	1m 50s
Cockpit — build all examples	2m 45s
Cockpit — build / test	2m 5s
Cockpit — deploy smoke dry-run	1m 14s
examples/ag-ui — e2e	3m 3s
Website — e2e	3m 16s
examples/chat — e2e (2/4)	2m 45s
examples/chat — e2e (3/4)	2m 26s
examples/chat — e2e (1/4)	4m 51s
Website — lint / build	1m 53s
Cockpit — secret-gated integration	4s
examples/chat — e2e (4/4)	2m 36s
Library — lint / test / build	3m 25s
Cockpit — e2e dispatcher	1m 21s
examples/chat — python smoke	1m 32s
PostHog — dashboards-as-code drift check	-1s
Cockpit — e2e (cockpit-ag-ui-client-tools-angular)	2m 45s
Cockpit — e2e (cockpit-ag-ui-tool-views-angular)	2m 27s
Cockpit — e2e (cockpit-ag-ui-json-render-angular)	2m 38s
Cockpit — e2e (cockpit-ag-ui-interrupts-angular)	2m 0s
Cockpit — e2e (cockpit-ag-ui-streaming-angular)	2m 46s
Cockpit — e2e (cockpit-ag-ui-a2ui-angular)	2m 7s
ag-ui demo → Vercel	0s
examples/chat — e2e	3s
Canonical demo → Vercel	0s
Cockpit — e2e	3s
CI — required	2s
Deploy → Vercel	0s
Production smoke	0s
	51m 49s

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