Add AGENTS.md

AGENTS.md

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+# AGENTS
+
+## Project summary
+- SunZones is a single-activity Android app (Jetpack Compose, Hilt, Room) for sunrise/sunset tracking across locations.
+
+## Build
+- Requires Java 17 + Android SDK.
+- Debug build: `./gradlew assembleDebug`
+
+## Release/version workflow
+- Run migration tests first. TODO: document the exact migration test command(s).
+- Update `CHANGELOG.md`, `README.md`, and versions in Gradle files.
+- Create a single git commit and push it.
+
+## Git workflow
+- Create a single git commit for current changes, then push it.