Bumps `@version` in `mix.exs` and the compiler's second carrier,
`@compiler_version` in `lib/statifier_blocks/compiler.ex`, to 0.28.0, and
the README install pin to `~> 0.28`. The compiler version moves on every
release because it is stamped into every compilation record, and in this
one compiled chart bytes DO move twice over - for a document with a
failure-classed final, and for a handler that captures by a payload path -
so a stored compiled chart or a pinned chart identity for either shape
must be re-captured.

Promotes the five `changelog.d/` fragments into a `## [0.28.0]` section
dated with the local date, grouped by heading and in fragment-name order
within each, and deletes them: sb-5ee4, sb-hykt, sb-ij80, sb-j0cz,
sb-m6ru. Every bullet is carried over byte for byte; the lead paragraph
and the link reference are the only prose written here.

A minor, not a patch, because two behaviours change and the lead paragraph
names them first. The reserved `<donedata>` param on a failure-classed
final is now `statifier_persistence:execution_status` rather than
`statifier_persistence:run_status`, which puts the durable-host floor at
`statifier_persistence >= 0.12`; and a capture pair whose source is absent
from the event payload no longer writes `:undefined`, leaving the
destination unwritten instead. Beside those it is additive: a literal
`["const", value]` capture source, a composite's own `outcomes`
declaration checked at Resolve, and a `run?` profile key that seats no run
at all.

No tag, no publish: both are the operator's.

Refs: sb-fct5