mkrootfs: emit complete inspect output

[brandonpayton]

Problem

mkrootfs inspect --format json called process.exit() as soon as the command promise resolved. Node could terminate before buffered stdout drained, so a 1,501-entry image produced only 65,536 of 198,111 bytes and invalid JSON.

Fix

• Set process.exitCode after command completion so normal event-loop shutdown drains stdout.
• Treat stdout EPIPE as a normal early-closing consumer, while leaving other stream errors visible.
• Cover both complete output above 64 KiB and an early-closing pipe through the real CLI shim.

Evidence

All commands ran through scripts/dev-shell.sh with Node 24.15.0.

Probe	Before	After
Large JSON stdout	65,536 bytes, invalid JSON	198,111 bytes, 1,501 parsed entries
head -c 1 consumer	exit 0, empty stderr	exit 0, empty stderr
Injected stdout EIO	error visible	exit 1, error visible

• Focused regressions: 2/2 passed.
• Full tools/mkrootfs suite: 135/135 passed.
• ES2024 TypeScript no-emit check: passed.
• Independent devil review: accepted the exact pushed commit and tree with no blocker, high, or medium findings.

Scope

This changes only CLI process shutdown and its tests. It does not change the Kandelo runtime, Node/browser host behavior, VFS format, ABI, packages, or release artifacts. Broad runtime and browser suites were not run because those paths are unaffected.

[github-actions]

Phase B-1 matrix build status — pr-920-staging

ABI v18. 5 built, 0 failed, 5 total.

Package	Arch	Status	Sha
rootfs	wasm32	built	d27191fb
shell	wasm32	built	8c8724d2
lamp	wasm32	built	af4ac801
node-vfs	wasm32	built	71c76ec3
wordpress	wasm32	built	08d29526

_{Auto-generated; replaced on each push. Raw data in the publish-status workflow artifact.}

[brandonpayton]

Replacement batch #921 preserves this PR exact patch as commit 2ffd72348 on merged ABI39 with an identical stable patch ID. Keep this PR open until the combined batch CI and maintainer review complete, then close it as superseded.

[brandonpayton]

Superseded by merged #921. This PR's head is patch-equivalent to main (git cherry reports '-'); #921 carries the complete mkrootfs inspect output draining as commit 2ffd723. No unique behavior or test remains unmerged.