feat(client): add validate_structured_output option to ClientSession #2531

Job	Run time
checks / readme-snippets	11s
checks / pre-commit	37s
checks / test (3.11, lowest-direct, windows-latest)	1m 15s
checks / test (3.12, locked, windows-latest)	1m 24s
checks / test (3.12, locked, ubuntu-latest)	52s
checks / test (3.10, locked, windows-latest)	1m 25s
checks / test (3.13, lowest-direct, ubuntu-latest)	52s
checks / test (3.12, lowest-direct, windows-latest)	1m 26s
checks / test (3.11, locked, ubuntu-latest)	50s
checks / test (3.11, locked, windows-latest)	1m 23s
checks / test (3.11, lowest-direct, ubuntu-latest)	53s
checks / test (3.14, lowest-direct, windows-latest)	1m 11s
checks / test (3.13, lowest-direct, windows-latest)	1m 18s
checks / test (3.14, lowest-direct, ubuntu-latest)	47s
checks / test (3.12, lowest-direct, ubuntu-latest)	58s
checks / test (3.10, locked, ubuntu-latest)	47s
checks / test (3.13, locked, windows-latest)	1m 13s
checks / test (3.14, locked, windows-latest)	2m 3s
checks / test (3.13, locked, ubuntu-latest)	45s
checks / test (3.10, lowest-direct, windows-latest)	1m 14s
checks / test (3.14, locked, ubuntu-latest)	1m 53s
checks / test (3.10, lowest-direct, ubuntu-latest)	52s
all-green	3s
	24m 12s

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