Add ergonomic Client class for testing MCP servers #123

Job	Run time
checks / readme-snippets	13s
checks / pre-commit	36s
checks / test (3.10, locked, ubuntu-latest)	46s
checks / test (3.10, locked, windows-latest)	2m 56s
checks / test (3.10, lowest-direct, ubuntu-latest)	45s
checks / test (3.11, lowest-direct, ubuntu-latest)	46s
checks / test (3.11, lowest-direct, windows-latest)	2m 29s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 11s
checks / test (3.12, lowest-direct, windows-latest)	3m 32s
checks / test (3.13, lowest-direct, ubuntu-latest)	45s
checks / test (3.11, locked, windows-latest)	2m 33s
checks / test (3.14, locked, ubuntu-latest)	2m 18s
checks / test (3.14, lowest-direct, windows-latest)	2m 24s
checks / test (3.13, locked, windows-latest)	2m 6s
checks / test (3.13, locked, ubuntu-latest)	42s
checks / test (3.12, lowest-direct, ubuntu-latest)	46s
checks / test (3.11, locked, ubuntu-latest)	47s
checks / test (3.12, locked, ubuntu-latest)	52s
checks / test (3.10, lowest-direct, windows-latest)	2m 26s
checks / test (3.13, lowest-direct, windows-latest)	2m 24s
checks / test (3.12, locked, windows-latest)	3m 20s
checks / test (3.14, locked, windows-latest)	3m 55s
all-green	4s
	38m 36s

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