Add MCP proxy helper #1760

Job	Run time
checks / pre-commit	34s
checks / readme-snippets	15s
checks / test (3.11, lowest-direct, windows-latest)	3m 27s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 4s
checks / test (3.11, lowest-direct, ubuntu-latest)	55s
checks / test (3.10, lowest-direct, windows-latest)	2m 41s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 12s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 5s
checks / test (3.12, locked, ubuntu-latest)	59s
checks / test (3.10, locked, windows-latest)	2m 29s
checks / test (3.10, locked, ubuntu-latest)	53s
checks / test (3.12, lowest-direct, windows-latest)	3m 39s
checks / test (3.14, locked, windows-latest)	3m 12s
checks / test (3.13, lowest-direct, ubuntu-latest)	56s
checks / test (3.12, locked, windows-latest)	3m 36s
checks / test (3.14, locked, ubuntu-latest)	2m 24s
checks / test (3.13, locked, ubuntu-latest)	51s
checks / test (3.14, lowest-direct, windows-latest)	3m 23s
checks / test (3.11, locked, ubuntu-latest)	54s
checks / test (3.13, locked, windows-latest)	3m 4s
checks / test (3.13, lowest-direct, windows-latest)	2m 50s
checks / test (3.11, locked, windows-latest)	2m 56s
all-green	5s
	43m 24s

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