v3.12.1

Patch. kj update output is clean again. A successful self-update now shows only the progress and result lines; npm's own noise — deprecation, allow-scripts and funding warnings — is build plumbing the user cannot act on, so it no longer reaches them.

Fixed

• kj update hides npm's warning noise on success (KJC-TSK-0612): the command captured npm's output instead of streaming it (stdio: "inherit" is gone). On success you see Current version → Updating → Updated to X; on failure the captured stdout/stderr IS surfaced so real errors (native build, permissions) stay diagnosable — never a silent failure. Extracted into a testable performSelfUpdate() in src/utils/update-check.js.