feat(spec): stamp flow-decision-mode-inclusive-explicit retiredAfter 17.4.0; pin the refusal list read before it

The entry landed with #15429 after this branch forked; it is in no published
tarball, so it carries the package label. The door still refuses it inside
its own per-entry window, because DEFAULT_FLIPS_NOT_REPLAYED_HERE is read first.

Claude-Session: https://claude.ai/code/session_01ARcDurZ5j34RdqsGgc4jgH
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

packages/metadata-core/src/artifact-forward-conversion.test.ts

@@ -619,6 +619,22 @@ describe('the artifact door never writes `mode: inclusive` onto an authored excl
     expect(Object.keys(registered.config ?? {}), 'what registration receives').not.toContain('mode');
   });
 
+  /**
+   * [#20390] The per-entry window does not reopen it either. The entry is
+   * stamped `retiredAfter: '17.4.0'`, so a ^17.4.0 floor on a runtime still
+   * labelled 17.4.0 is inside ITS per-entry window — and the door's refusal
+   * list is still read first, before any version is.
+   */
+  it('stays refused inside the per-entry window too — the refusal list is read before retiredAfter', () => {
+    const def = twoBranchDecisionDefinition('^17.4.0');
+    const result = applyArtifactForwardConversions(def, { runtimeSpecVersion: '17.4.0' });
+
+    // ⭐ ANTI-VACUITY: the per-entry window really is open on this input.
+    expect(result.verdict).toBe('converted-retired-after');
+    expect(verdictNodeOf(result.definition).config).toBeUndefined();
+    expect(result.notices.map((n) => n.conversionId)).not.toContain(ID);
+  });
+
   it('floor ^99.0.0 — the window is shut and nothing is replayed at all', () => {
     const def = twoBranchDecisionDefinition('^99.0.0');
     const result = applyArtifactForwardConversions(def, { runtimeSpecVersion: '17.4.0' });

packages/spec/src/conversions/registry.ts

@@ -12038,6 +12038,7 @@ const flowDecisionModeInclusiveExplicit: MetadataConversion = {
   id: 'flow-decision-mode-inclusive-explicit',
   toMajor: 18,
   retiredFromLoadPath: true,
+  retiredAfter: '17.4.0',
   surface: 'flow.nodes[].config.mode (decision)',
   summary:
     "edge-branched decision with two or more conditioned out-edges and no `mode`: `mode: 'inclusive'` written "