android: make AACP reconnect sessions control-safe

[beeemT]

Summary

This PR addresses the Android AACP control-connection lifecycle behind the AirPods Pro 3 press-and-hold failure reported in #690 and the related service-restart issue in #571.

It:

• resets shared AACP state before a new connection attempt;
• binds initialization, packet reads, and side effects to a connection generation and socket identity;
• cancels and closes stale readers, initialization jobs, and sockets;
• waits for the first valid AACP frame before replaying persistent control state;
• replays listening-mode availability, the Off option, and stem-action configuration for each fresh session; and
• emits the connected notification only after those configuration writes succeed.

The protocol notes explain why this matters: stem configuration is accessory state and must be overwritten when the AirPods connect to a new device (Configure Stem Long Press).

Root-cause model

The failure is consistent with overlapping AACP initialization/readers racing socket replacement. In that state, telemetry and direct listening-mode writes can continue working while the AirPods' physical stem configuration is stale or missing. The Android BLUETOOTH_PRIVILEGED warnings are not treated as the cause; the normal AACP socket and control path remain usable without root.

Validation

• Existing Android build completed successfully before this PR was opened.
• Tested on Pixel 10 Pro, Android 17, with AirPods Pro 3 model A3065.
• Clean connection: both stems worked.
• Force-stop/restart while Bluetooth remained connected: both stems worked.
• Bluetooth off/on reconnect: new session replayed configuration and both stems worked.
• Two rapid Bluetooth interruptions: stale sockets closed, fresh sessions replayed configuration, and both stems worked afterward.
• Observed listening-mode packets for values 01, 02, and 03 after reconnects.

Representative logs include:

AACP session 4 ready; persistent configuration sent: listeningModes=true, allowOffMode=true, stemConfig=true
AACP session 7 ready; persistent configuration sent: listeningModes=true, allowOffMode=true, stemConfig=true
socket closed (bytesRead = -1)
AACP session 10 ready; persistent configuration sent: listeningModes=true, allowOffMode=true, stemConfig=true

Scope and limitations

• This PR was generated using AI.
• The maintainer can use it as-is, adapt/cherry-pick parts of it, or use it only as inspiration for the correct fix to the AACP control-connection issue.
• Please review the lifecycle/concurrency design carefully before merging; this is not presented as guaranteed merge-ready code.
• The physical validation used the reviewed candidate APK, not the Play Store APK, and did not include an overnight soak or every custom stem-action mapping.

Related

• Related to [Android] AirPods Pro 3 press-and-hold stops working after reconnect #690 (new focused press-and-hold report)
• Related to service restart required to start sending/receiving data #571 (service restart / AACP initialization race)
• Android Bluetooth-stack context: Google Issue 371713238