Doc: Clarify MCP Client-Server model in What is MCP section #1942

Job	Run time
checks / readme-snippets	15s
checks / pre-commit	34s
checks / test (3.10, locked, windows-latest)	2m 24s
checks / test (3.10, lowest-direct, ubuntu-latest)	55s
checks / test (3.11, lowest-direct, windows-latest)	2m 50s
checks / test (3.12, lowest-direct, windows-latest)	3m 52s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 0s
checks / test (3.10, lowest-direct, windows-latest)	3m 7s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 21s
checks / test (3.11, locked, ubuntu-latest)	50s
checks / test (3.10, locked, ubuntu-latest)	54s
checks / test (3.11, locked, windows-latest)	2m 22s
checks / test (3.14, lowest-direct, windows-latest)	2m 27s
checks / test (3.12, locked, windows-latest)	3m 49s
checks / test (3.13, lowest-direct, ubuntu-latest)	55s
checks / test (3.13, locked, windows-latest)	2m 18s
checks / test (3.13, locked, ubuntu-latest)	50s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.13, lowest-direct, windows-latest)	2m 52s
checks / test (3.14, locked, windows-latest)	3m 3s
checks / test (3.12, locked, ubuntu-latest)	55s
checks / test (3.14, locked, ubuntu-latest)	2m 23s
all-green	4s
	41m 3s

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