feat: add reusable roots enforcement utilities to MCPServer #1831

Job	Run time
checks / pre-commit	30s
checks / readme-snippets	10s
checks / test (3.11, lowest-direct, windows-latest)	3m 9s
checks / test (3.10, lowest-direct, windows-latest)	2m 26s
checks / test (3.10, locked, ubuntu-latest)	52s
checks / test (3.13, lowest-direct, ubuntu-latest)	44s
checks / test (3.12, lowest-direct, ubuntu-latest)	50s
checks / test (3.10, lowest-direct, ubuntu-latest)	51s
checks / test (3.11, locked, ubuntu-latest)	50s
checks / test (3.12, lowest-direct, windows-latest)	3m 46s
checks / test (3.11, locked, windows-latest)	2m 35s
checks / test (3.13, locked, windows-latest)	2m 25s
checks / test (3.11, lowest-direct, ubuntu-latest)	46s
checks / test (3.10, locked, windows-latest)	2m 27s
checks / test (3.14, locked, windows-latest)	2m 56s
checks / test (3.14, lowest-direct, windows-latest)	2m 54s
checks / test (3.12, locked, windows-latest)	3m 3s
checks / test (3.13, lowest-direct, windows-latest)	2m 48s
checks / test (3.13, locked, ubuntu-latest)	47s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 9s
checks / test (3.12, locked, ubuntu-latest)	49s
checks / test (3.14, locked, ubuntu-latest)	2m 27s
all-green	5s
	39m 19s

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