Bumps @version to 0.10.0 and moves the README install pin to
`~> 0.10`. The minor is the outside-fail settlement seam: a linked
child failed from outside the interpreter now answers its parent's
pending `<invoke>`, and `Migrations.expected_version/0` is new
public surface.

Promotes changelog.d/sp-y7n.md and changelog.d/sp-b0g.md into a
`## [0.10.0] 2026-09-06` section, bullets carried over byte for
byte, and deletes both fragments.

Refs: sp-382