test: add SAF query android coverage

[ItzNotABug]

Summary

• Add connected Android tests that exercise Query-backed SAF listing through the real ExternalStorageProvider and DocumentsUI tree grant flow.
• Add an opt-in 5k SAF load test for larger fixtures with varied files, folders, nested content, query timing logs, and teardown cleanup.
• Add JVM contract coverage for select unioning, compound sort, repeated limit/offset, null-only in/notIn, booleans, and convenience query helpers.

Verification

• ./gradlew :dfc:assembleDebugAndroidTest :dfc:testDebugUnitTest :dfc:connectedDebugAndroidTest
• adb -s emulator-5554 shell am instrument -w -e class com.lazygeniouz.dfc.query.SafQueryLoadAndroidTest -e dfcSafLoad true com.lazygeniouz.dfc.test/androidx.test.runner.AndroidJUnitRunner
• git diff --check

Notes

• Stacked on Queries support #30 / queries-support.
• The load test is opt-in via dfcSafLoad=true so normal connected runs stay quick.