Remote comms: Cross-incarnation wake detection

[sirtimid]

Problem: The current wake detector only works within a single running process. If the kernel restarts while the system was asleep, we don't detect the time discontinuity and don't reset reconnection backoffs, causing unnecessary delays.

Expected Behavior:

• Store last known timestamp in persistent storage on shutdown
• On kernel startup, compare stored timestamp with current time
• If gap exceeds threshold (e.g., > 1 hour), treat as wake event and reset all reconnection backoffs
• Complement the existing runtime wake detector (installWakeDetector)

Implementation:

• Add timestamp storage to kernel store (e.g., lastNetworkActivityTimestamp)
• Write timestamp on initNetwork stop or periodically during operation
• Check timestamp on initNetwork startup
• If time gap > threshold, call reconnectionManager.resetAllBackoffs()
• Integrate with initNetwork or initRemoteComms startup sequence
• Consider edge cases: clock changes, timezone issues

Acceptance Criteria:

• Last timestamp is stored on shutdown
• Time discontinuity is detected on startup
• Backoffs are reset when discontinuity detected
• Works alongside runtime wake detector
• Tests verify cross-incarnation detection