Consume putio-sdk-kotlin from Maven Central instead of the composite build

[altaywtf]

Part of #14 (W2). Blocked by putdotio/putio-sdk-kotlin#43 (first v0.1.0 tag on Central).

Outcome

putio-android pins io.put:putio-sdk-kotlin:<version> and stops cloning the SDK as a sibling in CI, so an app SHA alone identifies the build.

Scope

• Replace the includeBuild wiring in settings.gradle.kts with a version-catalog dependency
• Drop the sibling checkout steps and SDK SHA recording from ci.yml and emulator-smoke.yml
• Update AGENTS.md toolchain, bootstrap.sh putioSdkKotlinPath handling, and the CI reproduction notes
• Keep a documented local override for developing against an SDK checkout

Acceptance criteria

• ./gradlew verify and both assembles green with no sibling checkout present