feat(client): add validate_structured_output option to ClientSession #2209

Job	Run time
checks / pre-commit	30s
checks / readme-snippets	10s
checks / test (3.11, locked, windows-latest)	2m 53s
checks / test (3.10, locked, windows-latest)	2m 33s
checks / test (3.12, lowest-direct, ubuntu-latest)	57s
checks / test (3.13, lowest-direct, ubuntu-latest)	54s
checks / test (3.10, lowest-direct, ubuntu-latest)	53s
checks / test (3.12, locked, ubuntu-latest)	57s
checks / test (3.12, locked, windows-latest)	5m 8s
checks / test (3.11, lowest-direct, ubuntu-latest)	54s
checks / test (3.12, lowest-direct, windows-latest)	2m 19s
checks / test (3.13, lowest-direct, windows-latest)	2m 43s
checks / test (3.14, lowest-direct, windows-latest)	2m 30s
checks / test (3.10, lowest-direct, windows-latest)	2m 27s
checks / test (3.11, locked, ubuntu-latest)	49s
checks / test (3.13, locked, ubuntu-latest)	55s
checks / test (3.13, locked, windows-latest)	2m 31s
checks / test (3.10, locked, ubuntu-latest)	55s
checks / test (3.11, lowest-direct, windows-latest)	2m 41s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 26s
checks / test (3.14, locked, ubuntu-latest)	2m 29s
checks / test (3.14, locked, windows-latest)	3m 57s
all-green	3s
	41m 34s

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