[codex] Prepare 0.4.0 onboarding release

[jasonacurry]

Summary

• bump the synced workspace, CLI, core, and schemas versions from 0.3.0 to 0.4.0
• add a 0.4.0 CLI changelog entry for the init-first onboarding release
• validate the release branch against the same checks the publish workflow relies on

Why

The merged onboarding update added new top-level CLI commands and materially changed the default first-run path, so this should ship as a minor release rather than a patch.

Validation

• pnpm lint
• pnpm typecheck
• pnpm check
• pnpm cli:smoke

Publish After Merge

After this PR merges to main, trigger .github/workflows/publish-npm.yml with:

• publish_target=all
• a ClawHub changelog describing the init-first onboarding flow and optional hosted follow-up
• the default ClawHub tags unless product positioning has changed

Do not publish 0.4.0 from this branch; publish from merged main.