fix(android): migrate aw-watcher-android-test buckets on startup

[TimeToBuildBob]

Summary

aw-server-rust#628 added migrateWatcherAndroidBucketNames(), but BackgroundService never called it. Upgrades from pre-rename builds keep writing/reading aw-watcher-android-test_* history that the Activity view no longer queries (#243).

This PR:

1. Declares the JNI and calls it during startup, after hostname migration so bucket IDs are stable first.
2. Guards with hasMigratedWatcherAndroidBucketNames. Completes the preference only when no aw-watcher-android-test* buckets remain. Collision leftovers retry on the next start instead of being marked done forever.
3. Extracts naming/completion rules into WatcherAndroidBucketMigration with JVM unit tests.

What this does not do

The current aw-server-rust submodule pin still uses UPDATE OR IGNORE. If both the legacy and canonical buckets exist, the rename is skipped. The SQL merge for that collision case is ActivityWatch/aw-server-rust#661. After that merges, bump this submodule — the Kotlin leftover check already matches the new merge (including partial overlap leftovers).

I did not bump the submodule in this PR: the merge commit is not yet on ActivityWatch/aw-server-rust, so a SHA bump would break CI checkout.

Tests

• WatcherAndroidBucketMigrationTest (canonical ID, leftover detection, success-prefix parsing)
• Datastore merge tests live on the rust PR

Refs

• Migration of existing databases #149
• Rename bucket "aw-watcher-android-test" to "aw-watcher-android"? #150
• Releases marked "pre-release" on github seem to be getting automatically pushed to the Play Store & auto-installed on devices #243
• fix(datastore): merge disjoint aw-watcher-android-test events on name collision aw-server-rust#661

[greptile-apps]

Greptile Summary

The PR invokes the existing native Android watcher-bucket migration during background-service startup and records completion only after confirming that no legacy bucket IDs remain.

• Adds a durable preference flag for successful migration completion.
• Runs hostname and watcher-bucket migrations on an I/O coroutine during service startup.
• Declares the native migration method and extracts bucket naming and completion rules.
• Adds JVM tests for canonical naming, legacy detection, completion, and native success parsing.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete blocking or independently actionable non-blocking defects identified.

The startup path invokes the migration off the main thread, preserves retries after native failures or collision leftovers, and marks completion only after the legacy bucket prefix is absent.

Important Files Changed

Filename	Overview
mobile/src/main/java/net/activitywatch/android/BackgroundService.kt	Adds asynchronous startup orchestration for the native watcher-bucket migration, retrying failures and collision leftovers.
mobile/src/main/java/net/activitywatch/android/AWPreferences.kt	Adds the durable completion marker that prevents rerunning a successfully completed watcher-bucket migration.
mobile/src/main/java/net/activitywatch/android/RustInterface.kt	Declares the Kotlin JNI entry point for the existing native watcher-bucket migration.
mobile/src/main/java/net/activitywatch/android/WatcherAndroidBucketMigration.kt	Encapsulates legacy ID recognition, canonicalization, native success parsing, and completion criteria.
mobile/src/test/java/net/activitywatch/android/WatcherAndroidBucketMigrationTest.kt	Covers the extracted migration naming, filtering, completion, and success-response rules.

Sequence Diagram

sequenceDiagram
    participant OS as Android
    participant Service as BackgroundService
    participant Prefs as AWPreferences
    participant Native as RustInterface
    OS->>Service: Start or recreate service
    Service->>Native: startServerTask()
    Service->>Prefs: Read migration flags
    opt Hostname migration pending
        Service->>Native: migrateHostname(deviceName)
        Native-->>Service: Migration result
        Service->>Prefs: Mark hostname migrated on success
    end
    opt Watcher bucket migration pending
        Service->>Native: migrateWatcherAndroidBucketNames()
        Native-->>Service: Migration result
        Service->>Native: getBucketsJSON()
        alt No legacy bucket IDs remain
            Service->>Prefs: Mark watcher migration complete
        else Legacy bucket IDs remain
            Service->>Service: Log and retry next startup
        end
    end

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_{Reviews (1): Last reviewed commit: "fix(android): call migrateWatcherAndroid..." | Re-trigger Greptile}

[TimeToBuildBob]

CI-green and mergeable (Greptile 5/5) — waiting only on a maintainer click.

This PR is ready to merge, but the bot has pull-only access to this repo and can't self-merge — surfacing it here so it isn't lost. The monitoring loop will stop re-flagging it now that this note is posted.