feat: migrate DeepSeek to @ai-sdk/deepseek + fix AI SDK tool streamin… #22254

Job	Run time
compile	7m 32s
check-openrouter-api-key	2s
knip	56s
platform-unit-test (windows-latest)	11m 21s
check-translations	52s
platform-unit-test (ubuntu-latest)	6m 28s
integration-test	4m 11s
	31m 22s

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