When the 24h session limit expires while the app is backgrounded,
onStop ends the session and stops replay. The subsequent onStart
was only calling startSession(), leaving replay disabled even
when session replay was active before the rotation. Mirror the
foreground-rotation branch by tracking whether replay was active
prior to rotation and restarting it under the new session.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

…close

Adds the missing PostHog-level test verifying that a caller-provided
$session_id wins over the session manager's value (the change in
165e5f2 had no integration test). Also clears the session listener
in PostHog.close() to avoid leaking the PostHog instance via the
process-singleton PostHogSessionManager, and simplifies a
?.also { it.invoke() } down to ?.invoke().

Addresses two points from @ioannisj's review:

- setSessionId now stamps sessionStartedAt so an externally-set
  session participates in the 24h expiry check. Without it,
  sessionStartedAt stayed 0 and the session would never expire.

- PostHogReplayIntegration.onSessionIdChanged now restarts the
  recording when the session rotates silently (e.g., 24h getter
  rotation), so the new session emits fresh meta + full wireframe
  events. Previously the new session received only incremental
  events, leaving the replay viewer with no baseline to render.
  If the session was cleared (background expiry), recording stops
  outright since snapshots without $session_id are dropped anyway.

The replay restart from onSessionIdChanged calls start(resumeCurrent=false)
which iterates a non-thread-safe WeakHashMap. The getter listener can fire
from any thread that calls capture(), so post both stop and start to the
main handler.

Also adds a PostHogTest that verifies the listener actually wires through:
forces an expired session via setSessionId + a backdated date provider,
calls getSessionId(), and asserts the fake replay handler's
onSessionIdChangedCalled flag flips. Drops a weak assertion from the
caller-provided session_id test that was tautologically true.

Closes the parity gap with iOS PostHogSessionManager that ioannisj
flagged. The Android session manager only rotated on background/
foreground transitions and on the 24h max-duration check; iOS also
rotates after 30min of no user activity, regardless of fg/bg state.

Manager changes:
- New sessionActivityTimestamp field tracking last activity.
- New touchSession() method mirroring iOS: rotates if idle past
  SESSION_INACTIVITY_DURATION (30min), else refreshes timestamp.
  No-op when backgrounded so background events don't keep a dead
  session alive.
- getActiveSessionId() also checks inactivity (in iOS order:
  inactivity first, then 24h max).
- Extracted isIdle/isMaxExpired/rotateLocked/clearLocked helpers
  to deduplicate the three places that compute expiry, and pulled
  the React Native check inside the lock to remove a TOCTOU race.

Wiring (call sites for touchSession):
- PostHog.capture(): touch at the start so any captured event
  counts as activity. iOS achieves this via UIEvent swizzling;
  Android lacks the equivalent so capture() is the safe fallback.
- PostHogLifecycleObserverIntegration.onStart: touch after
  setAppInBackground(false) (mirror iOS lifecycle hook).
- PostHogReplayIntegration.onTouchEventListener: touch on every
  intercepted touch (closest Android equivalent to iOS UIEvents).

The lifecycle observer's existing 30min Timer is now overlapping
with the manager's bg-clear path; kept as defense-in-depth for
backgrounded apps that don't fire any events.

Tests: added 7 unit tests for touchSession behavior, foreground
inactivity rotation, background inactivity clear, and the
no-op-while-backgrounded guarantee. Added a PostHog-level test
verifying that capture() rotates an idle session via touchSession
before reading the session id. Updated the existing
"under 24 hours" test to keep the session active with periodic
touches so the new inactivity check doesn't break it.