Add MCP proxy helper #1757

Job	Run time
checks / pre-commit	33s
checks / readme-snippets	14s
checks / test (3.10, lowest-direct, ubuntu-latest)	48s
checks / test (3.11, locked, windows-latest)	2m 42s
checks / test (3.10, locked, ubuntu-latest)	51s
checks / test (3.13, lowest-direct, ubuntu-latest)	44s
checks / test (3.12, locked, ubuntu-latest)	53s
checks / test (3.11, locked, ubuntu-latest)	46s
checks / test (3.11, lowest-direct, windows-latest)	3m 9s
checks / test (3.13, locked, ubuntu-latest)	43s
checks / test (3.13, locked, windows-latest)	4m 33s
checks / test (3.10, lowest-direct, windows-latest)	2m 41s
checks / test (3.12, lowest-direct, ubuntu-latest)	52s
checks / test (3.12, locked, windows-latest)	3m 48s
checks / test (3.12, lowest-direct, windows-latest)	3m 41s
checks / test (3.11, lowest-direct, ubuntu-latest)	44s
checks / test (3.14, locked, windows-latest)	3m 42s
checks / test (3.14, locked, ubuntu-latest)	2m 18s
checks / test (3.14, lowest-direct, windows-latest)	3m 0s
checks / test (3.13, lowest-direct, windows-latest)	3m 21s
checks / test (3.10, locked, windows-latest)	2m 36s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 9s
all-green	2s
	43m 50s

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