fix(reasoning): enforce confirmation-gated decision closure

- reconcileDecisionClosureOwnership normaliser between reconciliation and validation (Boundary B)
- Strips terminal parent updates without explicit user confirmation; preserves all other proposal work
- Strips parent from resolvedUnknownNodeIds bookkeeping on no-confirmation strip
- Restores reconciler-forced resolved→unknown for synthetic updates too
- Prevents hybrid unknown+value states by nulling newValue in all stripping paths
- No-op update created when reconciler synthesized the entry to prevent downstream errors

Prompt:
- Rule #143 rewritten from evidence-sufficiency to explicit-confirmation gate
- Directs model to use possibleInference for directional conclusions when confirmation absent

Regression preservation:
- 60B.43 lifecycle invariant restored via explicit confirmation phrases in fixture answers
- 60B.49 reconciliation auto-add invariant restored under confirmed closure flow
- Test apparatus fixed: structuralActionRequired required with userSupportedMeaning (validator constraint)

New coverage:
- 10 tests for all 60B.79/80 coverage requirements
- 5 prompt alignment tests for Rule #143

tests/graph/prompt-builder.test.js

@@ -863,6 +863,64 @@ describe("60B.4 decision materiality rule", () => {
   });
 });
 
+// ============================================
+// 60B.80 — explicit confirmation requirement in prompt
+// ============================================
+
+describe("60B.80 — prompt alignment for confirmation-gated closure", () => {
+  let sufficiencySection;
+
+  beforeAll(() => {
+    const testNode = makeNode({
+      id: "n-test-decision",
+      label: "Test Decision",
+      kind: "state",
+      status: "supported",
+    });
+    const prompt = buildGraphUpdatePrompt({
+      situationGraph: makeGraph({
+        centralStatement: "test",
+        nodes: [testNode],
+        edges: [],
+        activeUnknownNodeId: null,
+        resolvedNodeIds: [],
+        currentSummary: "Test.",
+      }),
+      situationContext: "Test context",
+    });
+    sufficiencySection = prompt.split("## Decision Sufficiency Rule")[1].split("## Decision Option Structure Rules")[0];
+  });
+
+  it("explicit confirmation requirement is present in the Decision Sufficiency Rule", () => {
+    expect(sufficiencySection).toContain("explicitly confirms");
+    expect(sufficiencySection).toContain("no other material uncertainty remains");
+  });
+
+  it("evidence-only terminal closure rule is replaced by confirmation-gated rule", () => {
+    // The OLD rule that permitted evidence-only closure is replaced:
+    expect(sufficiencySection).not.toContain(
+      "If the currently supported evidence is sufficient to distinguish the options and no such material unresolved factor remains, resolve the existing decision context",
+    );
+    // The NEW confirmation requirement is present:
+    expect(sufficiencySection).toContain("explicit confirmation");
+  });
+
+  it("model must not close parent merely because evidence appears sufficient", () => {
+    expect(sufficiencySection).toContain("You may not resolve the decision context unless");
+    expect(sufficiencySection).toContain("explicitly confirms (using their own words)");
+  });
+
+  it("preserves directional conclusion guidance when confirmation absent", () => {
+    expect(sufficiencySection).toContain("preserve your directional conclusion in possibleInference");
+  });
+
+  it("does NOT still permit evidence-only terminal closure", () => {
+    // The old "resolve" permission based on evidence sufficiency alone is gone:
+    const text = sufficiencySection;
+    expect(text).not.toContain("evidence is sufficient to distinguish the options and no such material unresolved factor remains, resolve");
+  });
+});
+
 // ============================================
 // 60B.11 — prompt prerequisite-aware targeting clarity
 // ============================================