Restore usage-example/ (not sample/) #80

User decision (2026-10-04, via the lead): sample/ goes back to its original name usage-example/. The user created usage-example/ in 2b91383 (2024-08-20). The rename to sample/ came only from the #62 proposal table and was never approved.

The Python sources stay where they are, under the new name: usage-example/src/commonMain/python (the app-template layout).

References to fix: settings.gradle.kts comment, CI (./gradlew -p sample, working-directory: sample, artifact paths, test-ios path filters), the Xcode phases (install-python-phase.sh, project.pbxproj), release scripts if any, AGENTS (§11 and §12 layout, §15/§16), PROJECT, SPEC, README en/ko, the guide, and the sample's own settings (rootProject.name), build file and catalog comments.

Done when nothing refers to sample/ and CI passes: consumer, android-e2e, desktop-e2e, test-ios, guide. Done on top of #79.