fix(mcpserver): omit unreturned TypedDict keys from structuredContent #3797

Job	Run time
checks / pre-commit	56s
checks / docs	53s
checks / readme-snippets	15s
checks / test (3.11, locked, windows-latest)	1m 58s
checks / test (3.12, locked, windows-latest)	1m 58s
checks / test (3.10, lowest-direct, windows-latest)	1m 53s
checks / test (3.12, lowest-direct, windows-latest)	1m 56s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 25s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 9s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 32s
checks / test (3.12, locked, ubuntu-latest)	1m 34s
checks / test (3.13, locked, windows-latest)	1m 30s
checks / test (3.10, locked, ubuntu-latest)	1m 23s
checks / test (3.14, locked, windows-latest)	1m 52s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 24s
checks / test (3.14, lowest-direct, windows-latest)	1m 45s
checks / test (3.13, locked, ubuntu-latest)	56s
checks / test (3.11, lowest-direct, windows-latest)	1m 56s
checks / test (3.10, locked, windows-latest)	1m 59s
checks / test (3.11, locked, ubuntu-latest)	1m 30s
checks / test (3.13, lowest-direct, ubuntu-latest)	1m 8s
checks / test (3.14, locked, ubuntu-latest)	1m 23s
checks / test (3.13, lowest-direct, windows-latest)	2m 16s
all-green	4s
	34m 35s

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