The zones suite's comments are shorter, with their reasons kept

[DevomB]

Part of the cleanup-held redo, after #241-#248. Comments only, in tools/image/zones-test.sh, a file that open PRs had held until the last batch.

How it was done. The same procedure as #242. Cleanup-held's change was merged onto main, and only regions where every changed line is a comment were kept. Each cut was then read by hand. Stripping comments from main's version and this one gives the same code, and bash -n passes.

Kept from the cut:

• The 3 GB guest: "not the default 2" becomes "not 2", with the reason (ephemeral-size-bound fills untrusted's 2G tmpfs, which is RAM) kept.
• Step 3's console copy: the guest's disk is not kept, so each suite's exit code, summary tail and FAIL rows go to the console.
• The accepted launcher gaps: the comment says only the gaps named below are accepted. Each one's reason (NETR, LC15/16, H1c) is in the pass message beside it, word for word.

Kept from main:

• The header and step list, lines 2-15, which --help prints. The cut's one-line header loses the suite's charter, and both its header and its step 3 rewrap would change the line count that sed -n '2,15p' relies on.
• The final mapper check, where the cut conflicted with main's newer check.

#245. f6's #245 changes only this file's verdict-list line (adding dhcpcd-separated), which this PR does not touch. f6 asked for this to land first.

How the run proves it. CI's shell lint covers the file. Nothing else changes.