fix(voip): prevent duplicate ringtone on Android incoming call

[diegolmello]

Proposed changes

Android VoIP pushes currently play two concurrent ringtones on incoming calls:

1. NotificationChannel (IMPORTANCE_HIGH + default ringtone URI + USAGE_NOTIFICATION_RINGTONE) — plays when the notification posts.
2. IncomingCallActivity.startRingtone() — plays RingtoneManager.getDefaultUri(...) via Ringtone.play() in onCreate.

Both fire simultaneously because the full-screen-intent notification posts and launches the activity in parallel, so the user hears overlapping / phasing audio.

This PR makes the NotificationChannel the sole ring source and adds setOnlyAlertOnce(true) as a safety net against same-notificationId reposts (e.g. FCM retries).

Design rationale

• Channel-owned ring is the Google-recommended pattern for call-style full-screen-intent notifications (matches Signal / WhatsApp).
• Channel sound still plays even on OEMs (MIUI, etc.) that silently block full-screen-intent activity launches — so dropping the activity-side ring does not regress reliability; it actually improves it.
• Accept/decline/timeout paths already call cancelById(notificationId) on every exit, so cancelling the notification reliably stops the channel audio.
• Pre-Android-O (API 24/25) keeps its existing builder.setSound(ringtoneUri) path (NotificationChannel doesn't exist on pre-O) — single source preserved there as well.

Files changed

• IncomingCallActivity.kt: remove startRingtone/stopRingtone methods, the ringtone field, all 7 call sites, and the now-unused Ringtone / RingtoneManager imports. Add a class-header KDoc noting that ring audio is owned by VoipNotification to prevent accidental reintroduction.
• VoipNotification.kt: add setOnlyAlertOnce(true) to the incoming-call NotificationCompat.Builder.

Full analysis + acceptance criteria + design options are in ~/plans/voip-android-duplicate-ring/plan.md (local-only, not committed).

Issue(s)

https://rocketchat.atlassian.net/browse/VMUX-76

How to test or reproduce

Before this PR (reproduction):

1. Trigger an incoming VoIP call to a device running feat.voip-lib-new.
2. Listen carefully — two ringtones overlap (audible phasing / echo). Record audio for clearer comparison.

After this PR (verification):

1. Smoke — locked screen: device locked → trigger VoIP push → single clean ringtone. Android 10, 12, 14.
2. Smoke — unlocked background: app backgrounded → push arrives → heads-up + FSI → single ring during transition.
3. Smoke — unlocked foreground: push arrives while app open → single ring via heads-up.
4. Accept stops audio: tap accept → ring cuts within ~300 ms.
5. Decline stops audio: tap decline → ring cuts immediately.
6. Timeout stops audio: let remainingLifetimeMs expire → ring cuts, notification cancelled.
7. Duplicate FCM push (same callId): re-send identical push → no re-alert (thanks to setOnlyAlertOnce(true)).
8. Busy-call guard regression: push while already in a call → rejectBusyCall fires, no ring (pre-existing behavior).
9. Pre-O emulator (API 24): verify ring still works via builder.setSound.

Screenshots

Not applicable — audio-only change.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves a current function)
• New feature (non-breaking change which adds functionality)
• Documentation update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• Lint and unit tests pass locally with my changes — Android-only change; local Kotlin compile could not run in this worktree (metro/symlink env issue). CI will verify. Recommend running yarn lint + ./gradlew :app:compileOfficialDebugKotlin on a full checkout.
• I have added tests that prove my fix is effective or that my feature works (if applicable) — No Kotlin unit tests exist in this repo. Requires manual on-device verification per "How to test" above.
• I have added necessary documentation (if applicable) — Added class-header KDoc in IncomingCallActivity.kt.
• Any dependent changes have been merged and published in downstream modules

Further comments

The change is net -27 lines (31 deletions, 4 insertions). No new logic added — all of the real work is removing redundant code and relying on the already-wired NotificationChannel audio path. No API changes, no state changes, no new dependencies.

Summary by CodeRabbit

• Bug Fixes
  • Improved incoming call audio alert handling to prevent duplicate ringtone sounds and vibrations when call notifications update.

[coderabbitai]

Walkthrough

Consolidated VoIP incoming call ringtone management from the activity layer to the notification layer. Removed direct ringtone playback/stop logic from IncomingCallActivity and added setOnlyAlertOnce(true) to the VoipNotification builder to prevent repeated alert sounds on notification updates.

Changes

Cohort / File(s)	Summary
Ringtone Management Refactoring android/app/src/main/java/chat/rocket/reactnative/voip/IncomingCallActivity.kt	Removed all ringtone field and playback/stop methods (startRingtone, stopRingtone). Ringtone responsibility now delegated to VoipNotification's NotificationChannel to prevent double-ringing.
Notification Alert Behavior android/app/src/main/java/chat/rocket/reactnative/voip/VoipNotification.kt	Added setOnlyAlertOnce(true) to notification builder to suppress repeated alert sounds and vibrations when the notification is updated.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Suggested labels

type: bug

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: removing duplicate ringtone playback on Android VoIP incoming calls by consolidating ring audio management.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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