Add ergonomic Client class for testing MCP servers #156

Job	Run time
checks / pre-commit	30s
checks / readme-snippets	11s
checks / test (3.10, locked, windows-latest)	2m 32s
checks / test (3.10, lowest-direct, ubuntu-latest)	45s
checks / test (3.11, lowest-direct, windows-latest)	2m 35s
checks / test (3.10, lowest-direct, windows-latest)	2m 19s
checks / test (3.11, lowest-direct, ubuntu-latest)	46s
checks / test (3.13, locked, windows-latest)	2m 24s
checks / test (3.14, lowest-direct, windows-latest)	2m 26s
checks / test (3.11, locked, ubuntu-latest)	45s
checks / test (3.13, locked, ubuntu-latest)	44s
checks / test (3.14, locked, ubuntu-latest)	2m 17s
checks / test (3.12, lowest-direct, ubuntu-latest)	49s
checks / test (3.11, locked, windows-latest)	2m 27s
checks / test (3.13, lowest-direct, ubuntu-latest)	46s
checks / test (3.12, lowest-direct, windows-latest)	3m 32s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.12, locked, ubuntu-latest)	52s
checks / test (3.13, lowest-direct, windows-latest)	2m 36s
checks / test (3.14, locked, windows-latest)	3m 22s
checks / test (3.10, locked, ubuntu-latest)	46s
checks / test (3.12, locked, windows-latest)	3m 18s
all-green	5s
	37m 52s

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