Add SSE response mode to the 2026 streamable-HTTP server entry #3117

Job	Run time
checks / pre-commit	45s
checks / docs	40s
checks / readme-snippets	15s
checks / test (3.11, lowest-direct, windows-latest)	1m 37s
checks / test (3.12, lowest-direct, windows-latest)	1m 30s
checks / test (3.10, locked, windows-latest)	1m 46s
checks / test (3.12, locked, ubuntu-latest)	1m 22s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 13s
checks / test (3.13, locked, windows-latest)	1m 57s
checks / test (3.14, locked, ubuntu-latest)	2m 10s
checks / test (3.10, lowest-direct, windows-latest)	1m 30s
checks / test (3.14, lowest-direct, windows-latest)	1m 47s
checks / test (3.13, locked, ubuntu-latest)	59s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 9s
checks / test (3.11, locked, ubuntu-latest)	1m 12s
checks / test (3.12, locked, windows-latest)	1m 40s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.11, locked, windows-latest)	1m 30s
checks / test (3.10, locked, ubuntu-latest)	1m 7s
checks / test (3.14, locked, windows-latest)	2m 20s
checks / test (3.13, lowest-direct, windows-latest)	1m 40s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 10s
all-green	2s
	31m 29s

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