chore: release v0.4.0

[github-actions]

🤖 New release

• tinybox: 0.3.1 -> 0.4.0 (⚠ API breaking changes)

⚠ tinybox breaking changes

--- failure inherent_method_missing: pub method removed or renamed ---

Description:
A publicly-visible method or associated fn is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.50.0/src/lints/inherent_method_missing.ron

Failed in:
  TinyBoxSized::as_ptr, previously in file /tmp/.tmpvdTgRV/tinybox/src/lib.rs:154

Changelog

0.4.0 - 2026-10-04

Fixed

• reduced UB
• use Layout::for_value_raw to avoid creating dangeling references

Other

• update pipeline
• automatic clippy fixes
• update github actions
• use sparse crates.io index
• update README.md

---

This PR was generated with release-plz.