feat: add fleet release closeout gate #150

Job	Run time
content-guard	6s
test (3.10)	18s
test (3.11)	18s
test (3.12)	32s
install-from-source (workspace+none, --depth workspace --harnesses none)	14s
install-from-source (repo+codex, --depth repo --harnesses codex)	15s
install-from-source (repo+claude, --depth repo --harnesses claude)	12s
install-from-source (kitchen-sink, --depth workspace --harnesses claude,codex,openclaw,hermes)	15s
install-from-source (workspace+claude+openclaw, --depth workspace --harnesses claude,openclaw)	13s
install-from-source (workspace+codex+openclaw, --depth workspace --harnesses codex,openclaw)	16s
install-from-source (repo+claude+publisher, --depth repo --harnesses claude --include publisher)	16s
	2m 55s

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