fix: correct MCPServer call_tool result type #2823

Job	Run time
checks / pre-commit	39s
checks / readme-snippets	13s
checks / test (3.10, locked, windows-latest)	1m 32s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 10s
checks / test (3.11, lowest-direct, windows-latest)	1m 27s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 4s
checks / test (3.11, locked, ubuntu-latest)	1m 1s
checks / test (3.12, locked, windows-latest)	1m 31s
checks / test (3.10, lowest-direct, windows-latest)	1m 21s
checks / test (3.11, locked, windows-latest)	1m 41s
checks / test (3.12, lowest-direct, windows-latest)	1m 57s
checks / test (3.12, locked, ubuntu-latest)	1m 7s
checks / test (3.10, locked, ubuntu-latest)	1m 1s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.14, lowest-direct, ubuntu-latest)	59s
checks / test (3.13, locked, ubuntu-latest)	55s
checks / test (3.14, locked, windows-latest)	2m 38s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 0s
checks / test (3.13, lowest-direct, windows-latest)	1m 35s
checks / test (3.14, locked, ubuntu-latest)	1m 59s
checks / test (3.13, locked, windows-latest)	1m 36s
checks / test (3.14, lowest-direct, windows-latest)	1m 22s
all-green	5s
	28m 55s

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