build(deps): bump msgspec from 0.20.0 to 0.21.0

[dependabot]

Bumps msgspec from 0.20.0 to 0.21.0.

Release notes

Sourced from msgspec's releases.

Version 0.21.0

• Fix a segfault on Python 3.13+ that could occur when creating structs that contained a __dict__, instead of only using __slots__ (#960).
• Improve type annotations for msgspec.UNSET (#975).
• Fix hashing of decoded tuples on Python 3.14 (#980).
• Add ref_template arg to msgspec.json.schema (#983).
• Add missing libm linkage to some architectures (#993).
• Fix memory leak when decoding sets (#991).
• Add uniqueItems annotation to set/frozenset JSON schemas (#984).
• BREAKING: Call __post_init__ from msgspec.structs.replace/copy.replace (#1000).

Changelog

Sourced from msgspec's changelog.

Version 0.21.0 (2026-04-08)

• Fix a segfault on Python 3.13+ that could occur when creating structs that contained a __dict__, instead of only using __slots__ ({pr}960).
• Improve type annotations for msgspec.UNSET ({pr}975).
• Fix hashing of decoded tuples on Python 3.14 ({pr}980).
• Add ref_template arg to msgspec.json.schema ({pr}983).
• Add missing libm linkage to some architectures ({pr}993).
• Fix memory leak when decoding sets ({pr}991).
• Add uniqueItems annotation to set/frozenset JSON schemas ({pr}984).
• BREAKING: Call __post_init__ from msgspec.structs.replace/copy.replace ({pr}1000).

Commits

• f99dca7 Update changelog for release 0.21.0 (#1001)
• f13b8cb Call __post_init__ from msgspec.structs.replace/copy.replace (#1000)
• 0b1ddd6 Improve __replace__ typing (#900)
• 30495ae Support custom enum metaclasses (#824)
• fe4ef5e Fix output path for generate_atof_consts.py (#981)
• 9fb6148 Make DecodeError and ValidationError inherit from ValueError (#790)
• f678049 Add ref_template param to mgspec.json.schema (#983)
• 83eaf0e fix DateTimeType docstring typo (#970)
• c01df28 Fix UnsetType truthiness narrowing in type stubs (#975)
• a5a5ca2 Fix segmentation fault on Python 3.13 (#960)
• Additional commits viewable in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot show <dependency name> ignore conditions will show all of the ignore conditions of the specified dependency
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)