chore: prepare 0.9.0 release

[cardmagic]

Sets 0.9.0 after merging #18, #19, #20, and #21.

Why a minor rather than a patch

Three additions to the public surface: WakeUpAdapters::Redis, adapter server_version and unsupported_server_reasons, and a new database_server doctor check that can warn where the doctor previously said nothing.

QA performed on main before bumping

Dimension	Result
SQLite, full rake	333 runs, 1187 assertions, 0 failures
PostgreSQL 17	333 runs, 0 failures
Rails 8.0 pin	333 runs, 0 failures
jsdom suite	26 pass
Real browser suite	5 pass
Standard, RuboCop, RBS, Steep, Brakeman	clean
gem build	0.9.0

MySQL was not run locally; CI covers it, along with the Redis job and the four-cell Ruby/Rails matrix.

Merge conflicts resolved along the way

Each of the four PRs edited docs/roadmap.md, and two edited CHANGELOG.md, so every rebase conflicted. Resolutions combined both sides rather than choosing one:

• feat: verify the database server at startup #19 needed docs: restore the compatibility CI milestone wording #18's corrected milestone wording and its own renumbering
• feat: add a Redis cross-process wake-up #20 removed a different milestone than feat: verify the database server at startup #19 had, so the list was renumbered sequentially rather than patched
• Every changelog conflict merged into a single Unreleased section; all entries were verified present afterwards

That renumbering churn is a consequence of a numbered milestone list. Worth considering unnumbered milestones later so parallel work stops colliding on line numbers.

[greptile-apps]

Greptile Summary

This PR prepares the 0.9.0 release by consistently updating the gem’s version metadata and converting the Unreleased changelog section into a dated release.

• Updates SolidObjects::VERSION from 0.8.0 to 0.9.0.
• Synchronizes the local gem version and checksum entry in Gemfile.lock.
• Labels the changelog entries as the 0.9.0 release dated 2026-08-10.

Confidence Score: 5/5

The PR appears safe to merge because all release metadata consistently identifies version 0.9.0.

The changes are limited to matching version and release-label updates, with no conditional, runtime, dependency, or security behavior introduced.

Important Files Changed

Filename	Overview
lib/solid_objects/version.rb	Updates the public gem version constant to 0.9.0 with no behavioral logic changes.
Gemfile.lock	Keeps both lockfile references to the local gem synchronized with version 0.9.0.
CHANGELOG.md	Finalizes the existing Unreleased entries under the dated 0.9.0 heading.

_{Reviews (1): Last reviewed commit: "chore: prepare 0.9.0 release" | Re-trigger Greptile}