test: qualify zero-byte host image write failures

docs/runtime-updates.mdmodified+9-5

Changes to docs/runtime-updates.md

		⋯644 linesShow the 644 lines above this hunk@@ -645,9 +645,13 @@ EIO, sync and physical power-loss campaigns open.
645	645
646	646	The opt-in [full-filesystem qualification](adr/0031-full-host-filesystem-fixture.md)
647	647	uses a separate private Linux mount namespace and a new bounded tmpfs for the
648		-actual store, candidates and slots. It targets real ENOSPC during the image copy
649		-and SQLite failure-state persistence, then exercises explicit metadata recovery,
	648	+actual store, candidates and slots. Separate cases leave either 1 MiB or zero
	649	+free bytes after actual ENOSPC filling. They require exactly a 1 MiB authenticated
	650	+prefix or an existing empty image file, with no runtime launch or health claim.
	651	+Both target real ENOSPC during the image copy and SQLite failure-state
	652	+persistence, then exercise explicit metadata recovery,
650	653	exact-slot abandonment and a fresh host trial in new processes. Retained file
651		-archives are copied and hashed before unmount. This additional campaign is in
652		-qualification; a local skip is not positive ENOSPC evidence. Physical-media,
653		-EDQUOT, EIO, sync and power-loss acceptance remain separate.
	654	+archives are copied and hashed before unmount. CI executes both cases; a local
	655	+skip is not positive ENOSPC evidence. Failure before any image bytes are written
	656	+does not establish behavior for a write syscall that returns zero without an
	657	+error. Physical-media, EDQUOT, EIO, sync and power-loss acceptance remain separate.