feat(correlation): add configurable delay before emitting orphan A events

New feature: Apache events can now wait for B events before being emitted as orphans.

Changes:
- Add ApacheEmitDelayMs config (default: 500ms)
- Add pendingOrphans structure for delayed emission
- processSourceA(): add A to pending orphans instead of immediate emission
- processSourceB(): check pending orphans before buffer A
- emitPendingOrphans(): emit orphans after delay expires
- Flush(): emit all pending orphans immediately (shutdown)

Configuration:
correlation:
  orphan_policy:
    apache_always_emit: true
    apache_emit_delay_ms: 500  # Wait 500ms before emitting as orphan

Backward compatibility:
- apache_emit_delay_ms: 0 → immediate emission (legacy mode)
- apache_emit_delay_ms < 0 → default 500ms

Tests added (5 new tests):
- TestCorrelationService_ApacheEmitDelay_BArrivesDuringDelay
- TestCorrelationService_ApacheEmitDelay_NoBArrives
- TestCorrelationService_ApacheEmitDelay_ZeroDelay
- TestCorrelationService_ApacheEmitDelay_MultipleA_SameKey
- TestCorrelationService_ApacheEmitDelay_Flush

All 30 tests pass. Coverage: 75.1%

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

internal/config/config.go

@@ -120,8 +120,9 @@ func (c *TimeWindowConfig) GetDuration() time.Duration {
 
 // OrphanPolicyConfig holds orphan event policy configuration.
 type OrphanPolicyConfig struct {
-	ApacheAlwaysEmit bool `yaml:"apache_always_emit"`
-	NetworkEmit      bool `yaml:"network_emit"`
+	ApacheAlwaysEmit   bool `yaml:"apache_always_emit"`
+	ApacheEmitDelayMs  int  `yaml:"apache_emit_delay_ms"` // Delay in ms before emitting orphan A
+	NetworkEmit        bool `yaml:"network_emit"`
 }
 
 // MatchingConfig holds matching mode configuration.
@@ -284,6 +285,14 @@ func (c *CorrelationConfig) GetApacheAlwaysEmit() bool {
 	return c.EmitOrphans
 }
 
+// GetApacheEmitDelayMs returns the delay in milliseconds before emitting orphan A events.
+func (c *CorrelationConfig) GetApacheEmitDelayMs() int {
+	if c.OrphanPolicy.ApacheEmitDelayMs > 0 {
+		return c.OrphanPolicy.ApacheEmitDelayMs
+	}
+	return domain.DefaultApacheEmitDelayMs // Default: 500ms
+}
+
 // GetMatchingMode returns the matching mode.
 func (c *CorrelationConfig) GetMatchingMode() string {
 	if c.Matching.Mode != "" {