Test fixes for MST metadata expectations and User-Agent env leak #2879

Job	Run time
check-linting (3.10)	2m 7s
check-linting (3.11)	2m 5s
check-types (3.14)	17m 32s
check-types (3.9)	2m 24s
check-types (3.11)	1m 58s
check-types (3.12)	2m 35s
check-linting (3.14)	16m 21s
check-linting (3.12)	1m 3s
check-types (3.13)	1m 23s
check-linting (3.9)	1m 11s
Unit Tests (Python 3.10, min deps)	3m 8s
Unit Tests (Python 3.11, min deps)	3m 10s
Unit Tests (Python 3.14, min deps)	17m 54s
Unit Tests (Python 3.14, default deps)	17m 57s
Unit Tests (Python 3.13, default deps)	2m 54s
check-linting (3.13)	1m 14s
Unit Tests + PyArrow (Python 3.9, default deps)	4m 7s
Unit Tests (Python 3.9, min deps)	3m 34s
Unit Tests + PyArrow (Python 3.10, min deps)	3m 59s
Unit Tests (Python 3.12, default deps)	2m 59s
Unit Tests (Python 3.9, default deps)	3m 37s
Unit Tests + PyArrow (Python 3.11, default deps)	3m 37s
check-types (3.10)	1m 11s
Unit Tests (Python 3.11, default deps)	2m 54s
Unit Tests + PyArrow (Python 3.9, min deps)	4m 0s
Unit Tests + PyArrow (Python 3.11, min deps)	4m 5s
Unit Tests (Python 3.10, default deps)	3m 36s
Unit Tests + PyArrow (Python 3.13, default deps)	3m 46s
Unit Tests + PyArrow (Python 3.10, default deps)	3m 38s
Unit Tests + PyArrow (Python 3.12, default deps)	3m 41s
Unit Tests + PyArrow (Python 3.14, default deps)	18m 31s
Unit Tests + PyArrow (Python 3.14, min deps)	20m 9s
	3h 2m 20s

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