[selnaklavu]

• The NATIVE agent hashes the APK the app runs from (ApplicationInfo.sourceDir) once per process, before the first dial, and sends buildId = apk-sha256:<64 lowercase hex> in AUTH, with sdkBuild = <versionName>(<versionCode>).
• Both fields are left out when there is nothing to send; the rest of the AUTH line is unchanged, byte for byte.
• Servers on main ignore the new fields. The BINARY engine is not touched.
• Unit tests cover the hash, the per-process cache and the AUTH line. The instrumented e2e passes with the fields on, and the hash the agent sent equals the SHA-256 of the installed APK.