fix(litigationplanner): respect trigger_event_id + suppress optional from default (yoUPC#178 + #2568/#2570)

Two paired engine semantics fixes:

1. trigger_event_id is now the authoritative semantic anchor. When a
   rule carries trigger_event_id, the engine no longer falls back to
   the proceeding's trigger date — it resolves the anchor via
   CalcOptions.TriggerEventAnchors keyed by paliad.trigger_events.code.
   Missing anchor renders the rule as IsConditional (empty date) and
   propagates via courtSet so descendants also surface as conditional.
   Fixes the RoP.109.5 bug where the engine fabricated a date 2 weeks
   before the user's SoC instead of waiting for the oral_hearing date.

2. priority='optional' rules are suppressed from the default
   Calculate output. Callers (paliad /tools/procedures,
   youpc.org/deadlines) opt in via CalcOptions.IncludeOptional=true to
   restore the legacy "show optional applications" behaviour. The
   suppression cascades through skippedIDs so child rules drop too.

Wire shape additions:

  - CalcOptions.IncludeOptional bool
  - CalcOptions.TriggerEventAnchors map[string]string
  - Timeline.RulesAwaitingAnchor int (count of suppressed-by-missing-
    anchor rules, for caller telemetry / "N rules need an anchor" UX)

Existing before-court-set-anchor tests opt in to IncludeOptional=true
to preserve their non-optional-related test intent.

Refs: youpcorg/head delegations #2568 + #2570, m/paliad#153 (Litigation
Builder PRD path).

pkg/litigationplanner/engine.go

@@ -80,6 +80,21 @@ func Calculate(
 		overrideDates[code] = od
 	}
 
+	// Trigger-event anchors keyed by paliad.trigger_events.code
+	// (t-paliad-342). Parsed up-front so malformed dates error before
+	// the rule walk. When a rule has trigger_event_id set, the engine
+	// looks up triggerAnchorByCode[trigger_event.code] for the
+	// semantic anchor instead of falling back to the proceeding's
+	// trigger date.
+	triggerAnchorByCode := make(map[string]time.Time, len(opts.TriggerEventAnchors))
+	for code, dateStr := range opts.TriggerEventAnchors {
+		td, err := time.Parse("2006-01-02", dateStr)
+		if err != nil {
+			return nil, fmt.Errorf("invalid trigger event anchor for %q (%q): %w", code, dateStr, err)
+		}
+		triggerAnchorByCode[code] = td
+	}
+
 	// Look up proceeding type metadata.
 	pickedProceeding, rules, err := catalog.LoadProceeding(ctx, proceedingCode, opts.ProjectHint)
 	if err != nil {
@@ -213,6 +228,7 @@ func Calculate(
 	perCardAppellant := opts.PerCardAppellant
 	skippedIDs := make(map[uuid.UUID]struct{}, len(skipRules))
 	hiddenCount := 0
+	rulesAwaitingAnchor := 0
 	appellantContext := make(map[uuid.UUID]string, len(rules))
 
 	for _, r := range walkRules {
@@ -227,6 +243,17 @@ func Calculate(
 			continue
 		}
 
+		// Optional-rule suppression (t-paliad-342 / youpcorg#2570).
+		// Rules tagged priority='optional' don't auto-fire in the
+		// default timeline; the caller opts in via
+		// CalcOptions.IncludeOptional. Cascade through skippedIDs so
+		// children chaining off the suppressed rule also drop — they
+		// can't compute a date against a missing parent.
+		if r.Priority == "optional" && !opts.IncludeOptional {
+			skippedIDs[r.ID] = struct{}{}
+			continue
+		}
+
 		// SkipRules suppression (t-paliad-265).
 		// t-paliad-290 (m/paliad#122): when opts.IncludeHidden is set,
 		// we re-surface the directly-skipped row (faded via IsHidden)
@@ -327,15 +354,43 @@ func Calculate(
 		// (m/paliad#126 / t-paliad-294). When a rule has a real
 		// trigger_event_id, that catalog event is the actual semantic
 		// anchor — not the parent_id node, which is only the calc-time
-		// arithmetic anchor. Only the user-facing wire fields shift;
-		// parentRule (and the parent_id chain feeding parentIsCourtSet
-		// and the calc-time arithmetic below) stays anchored on the
-		// rule tree.
+		// arithmetic anchor. Only the user-facing wire fields shift
+		// here; the calc-time anchor logic for trigger_event_id rules
+		// lives just below.
+		var triggerEventAnchor time.Time
+		var hasTriggerEventAnchor bool
 		if r.TriggerEventID != nil {
 			if te, ok := triggerEventByID[*r.TriggerEventID]; ok {
 				d.ParentRuleCode = te.Code
 				d.ParentRuleName = te.NameDE
 				d.ParentRuleNameEN = te.Name
+				if td, ok := triggerAnchorByCode[te.Code]; ok {
+					triggerEventAnchor = td
+					hasTriggerEventAnchor = true
+				}
+			}
+
+			// Trigger-event semantic-anchor suppression (t-paliad-342 /
+			// youpcorg#2568). When a rule has an explicit trigger_event_id
+			// but the caller hasn't supplied a date for that event via
+			// CalcOptions.TriggerEventAnchors, the engine refuses to
+			// fabricate a date off the proceeding's trigger date — the
+			// rule's semantic anchor is the event itself, not the SoC.
+			// Render IsConditional with empty dates and propagate via
+			// courtSet so descendants chaining off this rule also surface
+			// as conditional rather than projecting fictional dates.
+			if !hasTriggerEventAnchor {
+				d.IsConditional = true
+				d.IsCourtSet = true
+				d.DueDate = ""
+				d.OriginalDate = ""
+				courtSet[r.ID] = true
+				rulesAwaitingAnchor++
+				if r.SubmissionCode != nil {
+					skippedIDs[r.ID] = struct{}{}
+				}
+				deadlines = append(deadlines, d)
+				continue
 			}
 		}
 
@@ -379,6 +434,20 @@ func Calculate(
 				}
 			}
 
+			// Trigger-event anchor wins over the bucket logic below: a
+			// zero-duration rule with trigger_event_id is "occurs on the
+			// trigger event's date". Anchor missing was already caught
+			// above (suppression branch).
+			if hasTriggerEventAnchor {
+				d.DueDate = triggerEventAnchor.Format("2006-01-02")
+				d.OriginalDate = d.DueDate
+				if r.SubmissionCode != nil {
+					computed[*r.SubmissionCode] = triggerEventAnchor
+				}
+				deadlines = append(deadlines, d)
+				continue
+			}
+
 			if r.ParentID == nil && !r.IsCourtSet {
 				// Bucket 1: timeline anchor.
 				d.IsRootEvent = true
@@ -457,11 +526,19 @@ func Calculate(
 			continue
 		}
 
-		// Anchor: prefer alt-anchor (e.g. priority_date for
-		// epa.grant.exa publish) when supplied, then parent's computed
-		// date (or user override), then trigger date.
+		// Anchor priority:
+		//   1. trigger_event_id semantic anchor (t-paliad-342) — when
+		//      the rule has trigger_event_id and the caller supplied a
+		//      date in TriggerEventAnchors, that date wins over the
+		//      parent chain AND the priority_date alt-anchor. The
+		//      missing-anchor case was already short-circuited above.
+		//   2. priority_date alt-anchor (epa.grant.exa publish).
+		//   3. parent's computed date (or user override).
+		//   4. proceeding trigger date (default fallback).
 		baseDate := triggerDate
-		if r.AnchorAlt != nil && *r.AnchorAlt == "priority_date" && priorityDate != nil {
+		if hasTriggerEventAnchor {
+			baseDate = triggerEventAnchor
+		} else if r.AnchorAlt != nil && *r.AnchorAlt == "priority_date" && priorityDate != nil {
 			baseDate = *priorityDate
 		} else if r.ParentID != nil {
 			for _, prev := range rules {
@@ -635,12 +712,13 @@ func Calculate(
 	}
 
 	resp := &Timeline{
-		ProceedingType:   pickedProceeding.Code,
-		ProceedingName:   pickedProceeding.Name,
-		ProceedingNameEN: pickedProceeding.NameEN,
-		TriggerDate:      triggerDateStr,
-		Deadlines:        deadlines,
-		HiddenCount:      hiddenCount,
+		ProceedingType:      pickedProceeding.Code,
+		ProceedingName:      pickedProceeding.Name,
+		ProceedingNameEN:    pickedProceeding.NameEN,
+		TriggerDate:         triggerDateStr,
+		Deadlines:           deadlines,
+		HiddenCount:         hiddenCount,
+		RulesAwaitingAnchor: rulesAwaitingAnchor,
 	}
 	// Sub-track routing keeps the user-picked proceeding's identity,
 	// so the trigger-event label rides on `pickedProceeding`.