Related Issue

No linked issue; this fixes startup automatic updates delaying installation until the next launch.

Problem

Automatic updates reused the notification-oriented cache flow: when the cache was empty, startup refreshed the latest-version cache in the background, but the freshly discovered version was not considered for installation until the next CLI launch.

What changed

• Start the detached automatic installer from the fresh startup update check when it discovers a newer version.
• Reuse the existing active-install, failure-threshold, preference, lock, telemetry, and logging paths for both cached and fresh update checks.
• Add regression coverage for first-check installation, disabled automatic updates, and non-interactive startup.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

Validation

• pnpm exec vitest run apps/kimi-code/test/cli/update/preflight.test.ts
• pnpm --filter @moonshot-ai/kimi-code run typecheck
• pnpm exec oxlint --type-aware apps/kimi-code/src/cli/update/preflight.ts apps/kimi-code/test/cli/update/preflight.test.ts
• git diff --check