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/before_court_set_anchor_test.go

@@ -205,7 +205,11 @@ func TestCalculate_BeforeChildOfCourtSetParent_OutOfOrderSequence(t *testing.T)
 
 	cat := &stubCatalog{pt: pt, rules: rules}
 
-	timeline, err := Calculate(ctx, "upc.inf.cfi", "2026-05-26", CalcOptions{}, cat, noOpHolidays{}, fixedCourts{})
+	// IncludeOptional=true because translation_request carries
+	// priority='optional'; the test exercises the before-child-of-
+	// court-set-parent flow, which is orthogonal to the optional-rule
+	// suppression added in t-paliad-342.
+	timeline, err := Calculate(ctx, "upc.inf.cfi", "2026-05-26", CalcOptions{IncludeOptional: true}, cat, noOpHolidays{}, fixedCourts{})
 	if err != nil {
 		t.Fatalf("Calculate: %v", err)
 	}
@@ -301,8 +305,10 @@ func TestCalculate_BeforeChildOfCourtSetParent_WithOverride(t *testing.T) {
 
 	cat := &stubCatalog{pt: pt, rules: rules}
 
-	// User pins the oral hearing to 2026-10-15.
+	// User pins the oral hearing to 2026-10-15. IncludeOptional=true
+	// because translation_request is priority='optional' (t-paliad-342).
 	opts := CalcOptions{
+		IncludeOptional: true,
 		AnchorOverrides: map[string]string{
 			oralCode: "2026-10-15",
 		},