fix: a re-plan drops the holes it invalidated and restarts the tick they are addressed by

rebuild_locked() replaced the store, so produced() restarted at 0 while the
producer's tick_ kept counting: a hole's slot and tick addressing then described
a buffer that was gone, forget_holes_before() could not retire it, and a
backfill's amend fell outside the ring -- repairing nothing while the hole was
still marked repaired, which is the band reporting the opposite of the truth. A
re-plan generation is the signal rather than the stride/channel-count guard,
which a reconnect with an identical CONFIG leaves unchanged. slot_base_ is left
alone: it is relative mode's clock origin and must not walk backwards when the
user retypes the window.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/acquisition.hpp

@@ -127,6 +127,10 @@ class Acquisition {
   /// Warn-once latch for a loss past the reservation cap. A member, not a function-local
   /// `static`, matching the latch Task 2 added for the same reason.
   bool warned_outage_ = false;
+  /// The re-plan generation this object last reacted to. The buffer is re-planned whenever the
+  /// model rebuilds it, and the state tied to the old store (`tick_` and the accumulators) is
+  /// reset when this falls behind `ScopeModel::plan_generation()`.
+  unsigned seen_plan_generation_ = 0;
   std::vector<double> stamps_;
   std::vector<double> abs_stamps_;
   /// The decimation filter's state: a running sum per channel (and one for the shared