Add multi-tenancy TODO comments across MCP Python SDK codebase #3260

Job	Run time
checks / pre-commit	29s
checks / readme-snippets	10s
checks / test (3.10, lowest-direct, windows-latest)	1m 34s
checks / test (3.11, highest, ubuntu-latest)	33s
checks / test (3.11, lowest-direct, windows-latest)	1m 31s
checks / test (3.10, highest, ubuntu-latest)	37s
checks / test (3.11, lowest-direct, ubuntu-latest)	38s
checks / test (3.12, lowest-direct, ubuntu-latest)	34s
checks / test (3.10, highest, windows-latest)	1m 23s
checks / test (3.10, lowest-direct, ubuntu-latest)	38s
checks / test (3.13, lowest-direct, windows-latest)	1m 36s
checks / test (3.11, highest, windows-latest)	1m 56s
checks / test (3.12, highest, ubuntu-latest)	36s
checks / test (3.12, highest, windows-latest)	1m 17s
checks / test (3.13, highest, ubuntu-latest)	34s
checks / test (3.13, highest, windows-latest)	1m 29s
checks / test (3.13, lowest-direct, ubuntu-latest)	36s
checks / test (3.12, lowest-direct, windows-latest)	1m 29s
	17m 40s

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