feat(agentos): publish the default software list

[eersnington]

• The default software list now lives in one file, software/default-software.json. Core's runtime, Core's build staging, and publish all read it instead of keeping their own copies.
• Publish now writes default-software.json next to manifest.json in the software artifacts: the default packages (coreutils, sed, grep, gawk, findutils, diffutils, tar, gzip) with their path, digest, and size, in install order.
• Publish fails if a default package is missing from the software catalog.
• Services reads this list to install default software in hosted VMs, so hosted and embedded VMs get the same commands.

{
	"schemaVersion": 1,
	"artifacts": [
		{ "name": "coreutils", "digest": "sha256:…", "size": 66780710, "path": "packages/coreutils/<sha256>.aospkg" },
		…
	]
}

Code: software/default-software.json, scripts/publish/src/lib/software-artifacts.ts, packages/core/src/default-software.ts, packages/core/scripts/stage-default-software.mjs

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[the-company-company]

🟠 1 medium-severity finding

_{Reviewed commit 74b0c90.}

[the-company-company]

✅ No issues found

_{Reviewed commit c32840f.}