Add MCP proxy helper #1759

Job	Run time
checks / readme-snippets	10s
checks / pre-commit	38s
checks / test (3.11, locked, ubuntu-latest)	47s
checks / test (3.14, lowest-direct, windows-latest)	2m 59s
checks / test (3.11, lowest-direct, windows-latest)	2m 34s
checks / test (3.10, locked, windows-latest)	2m 42s
checks / test (3.12, locked, ubuntu-latest)	47s
checks / test (3.11, lowest-direct, ubuntu-latest)	49s
checks / test (3.13, lowest-direct, windows-latest)	3m 15s
checks / test (3.10, lowest-direct, windows-latest)	2m 42s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.12, lowest-direct, ubuntu-latest)	48s
checks / test (3.11, locked, windows-latest)	2m 57s
checks / test (3.13, lowest-direct, ubuntu-latest)	52s
checks / test (3.13, locked, windows-latest)	2m 19s
checks / test (3.10, lowest-direct, ubuntu-latest)	48s
checks / test (3.10, locked, ubuntu-latest)	51s
checks / test (3.12, locked, windows-latest)	3m 58s
checks / test (3.13, locked, ubuntu-latest)	42s
checks / test (3.12, lowest-direct, windows-latest)	3m 38s
checks / test (3.14, locked, windows-latest)	3m 45s
checks / test (3.14, locked, ubuntu-latest)	2m 15s
all-green	5s
	41m 45s

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