refactor: what counts as an event moves into its own evaluator, so a search can ask the same question the trigger asks

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

src/trigger.hpp

@@ -6,10 +6,9 @@
 #include <cstdint>
 #include <string>
 
-namespace udpscope {
+#include "condition.hpp"
 
-/// Which way the trigger signal crosses the level.
-enum class TriggerEdge { Rising, Falling, Both };
+namespace udpscope {
 
 /// How an armed trigger re-arms after it fired.
 enum class TriggerMode { Normal, Single };
@@ -24,8 +23,10 @@ struct TriggerConfig {
   bool enabled = false;          ///< trigger mode on/off (toolbar).
   bool armed = false;            ///< arm/disarm button.
   int channel = -1;              ///< index into ScopeModel::channels(), -1 = none.
-  double level = 0.0;
-  TriggerEdge edge = TriggerEdge::Rising;
+  /// What counts as an event on that channel: the level and edge, and for the qualified
+  /// shapes the width, band or timeout as well. The engine does not interpret it -- it
+  /// hands it to an `EventDetector`.
+  EventCondition condition{};
   double pretrigger_pct = 50.0;  ///< share of the buffer shown before the event.
   double holdoff_s = 0.010;      ///< default from the spec.
   TriggerMode mode = TriggerMode::Normal;
@@ -92,8 +93,8 @@ class TriggerEngine {
   /// pre-trigger window an edge needs before it may open a capture.
   double history() const noexcept { return last_t_s_ - oldest_s_; }
   double pre_seconds() const noexcept { return pre_seconds_; }
-  double last_value() const noexcept { return prev_; }
-  bool have_last() const noexcept { return have_prev_; }
+  double last_value() const noexcept { return detector_.last_value(); }
+  bool have_last() const noexcept { return detector_.have_last(); }
   double last_t() const noexcept { return last_t_s_; }
   double holdoff_until() const noexcept { return holdoff_until_s_; }
 
@@ -107,8 +108,9 @@ class TriggerEngine {
   TriggerConfig cfg_{};
   std::string channel_name_;  ///< the trigger channel's stable identity (see `configure`).
   bool armed_ = false;
-  bool have_prev_ = false;
-  double prev_ = 0.0;
+  /// What an event *is*. The engine owns when one may open a capture; this owns whether
+  /// the sample is one at all.
+  EventDetector detector_{};
   bool pending_ = false;      ///< an edge was seen; collecting the post window
   double pending_start_s_ = 0.0;
   double holdoff_until_s_ = 0.0;