fix: explain transport host rejections #2366

Job	Run time
checks / readme-snippets	11s
checks / pre-commit	34s
checks / test (3.10, locked, ubuntu-latest)	1m 7s
checks / test (3.11, lowest-direct, windows-latest)	3m 21s
checks / test (3.10, lowest-direct, ubuntu-latest)	1m 3s
checks / test (3.10, locked, windows-latest)	2m 41s
checks / test (3.11, lowest-direct, ubuntu-latest)	1m 2s
checks / test (3.12, lowest-direct, windows-latest)	4m 1s
checks / test (3.10, lowest-direct, windows-latest)	3m 6s
checks / test (3.12, lowest-direct, ubuntu-latest)	1m 7s
checks / test (3.11, locked, windows-latest)	2m 26s
checks / test (3.13, lowest-direct, windows-latest)	2m 49s
checks / test (3.13, locked, ubuntu-latest)	59s
checks / test (3.11, locked, ubuntu-latest)	1m 4s
checks / test (3.14, lowest-direct, windows-latest)	2m 26s
checks / test (3.12, locked, windows-latest)	3m 37s
checks / test (3.14, lowest-direct, ubuntu-latest)	1m 26s
checks / test (3.13, locked, windows-latest)	2m 46s
checks / test (3.12, locked, ubuntu-latest)	1m 5s
checks / test (3.14, locked, ubuntu-latest)	2m 34s
checks / test (3.14, locked, windows-latest)	3m 19s
checks / test (3.13, lowest-direct, ubuntu-latest)	53s
all-green	2s
	43m 39s

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