fix(adapter): resolve all WHYNOT-WP-0002 drift — designbook-refresh green

Triage the three surfaced divergences the governance-correct way (no stack->React
back-edit, no ir/ hand-edit); make adapt-lit/parity-lit/designbook-refresh now
exit 0:

- PipelineStrip: documented TAG_OVERRIDES in scripts/ir-extract.mjs maps the
  React 'PipelineStrip' to the established tag wn-pipeline (the web-component tag
  is an IR-projection detail, not React-dictated; the component name stays
  faithful). Tag now matches the element; parity tests it (no longer skipped).
- PageHeader.actions: the drift detector now collects each element's named slots
  and treats an IR prop honoured by a same-named slot (<slot name="actions">) as
  satisfied (prop-via-slot, informational) rather than prop-missing.
- Sidebar.current: recorded as an auditable accepted divergence in
  adapters/lit/drift.accepted.json (React monolithic 'current' key vs Lit per-item
  'active' on composable <wn-sidebar-item>) — listed, downgraded to info, not gated.

Rendered surfaces (src/, examples/) untouched — verified zero diff; parity renders
all 10 components green. Adapt/parity outputs idempotent (stable re-run).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

adapters/lit/scaffold.mjs

@@ -57,6 +57,13 @@ function classProps(name, classes) {
   return { ...inherited, ...own };
 }
 
+function classSlots(name, classes) {
+  const cls = classes[name];
+  if (!cls) return new Set();
+  const inherited = cls.extends && classes[cls.extends] ? classSlots(cls.extends, classes) : new Set();
+  return new Set([...inherited, ...(cls.slots || [])]);
+}
+
 export function parseLitElements(repo) {
   const classes = {}; // className → { propsBlock, extends, file }
   const defines = []; // { tag, className, file }
@@ -74,13 +81,17 @@ export function parseLitElements(repo) {
       const nextClass = src.indexOf("class ", m.index + m[0].length);
       const propsBlock = propsAt !== -1 && (nextClass === -1 || propsAt < nextClass)
         ? balancedBlock(src, propsAt) : null;
-      classes[className] = { propsBlock, extends: base, file };
+      // Named slots the element renders (e.g. <slot name="actions">) — a prop can
+      // be honoured by a same-named slot rather than a reactive property.
+      const region = src.slice(m.index, nextClass === -1 ? undefined : nextClass);
+      const slots = [...region.matchAll(/<slot\s+name="([\w-]+)"/g)].map((x) => x[1]);
+      classes[className] = { propsBlock, extends: base, file, slots };
     }
     const defRe = /customElements\.define\(\s*["']([\w-]+)["']\s*,\s*([A-Za-z_$][\w$]*)\s*\)/g;
     while ((m = defRe.exec(src))) defines.push({ tag: m[1], className: m[2], file });
   }
   const byTag = {};
-  for (const d of defines) byTag[d.tag] = { ...d, props: classProps(d.className, classes) };
+  for (const d of defines) byTag[d.tag] = { ...d, props: classProps(d.className, classes), slots: classSlots(d.className, classes) };
   return byTag;
 }
 
@@ -96,8 +107,28 @@ export function litAttrOf(decl) {
   return decl.attribute === false ? null : decl.attribute;
 }
 
-function classify(issues) {
-  for (const i of issues) i.severity = ACTIONABLE.has(i.kind) ? "drift" : "info";
+// Human-curated accepted divergences — the auditable output of drift triage for
+// divergences that are intentional (e.g. a React monolithic prop modelled
+// per-child in a composable Lit element). Keyed `<Component>:<kind>:<prop>` → rationale.
+// Read from adapters/lit/drift.accepted.json. An accepted issue is still listed in
+// the report (marked "accepted: <why>") but downgraded to info, so it does not gate.
+export function loadAccepted(repo) {
+  const path = join(repo, "adapters", "lit", "drift.accepted.json");
+  if (!existsSync(path)) return {};
+  try {
+    const out = {};
+    for (const e of (JSON.parse(readFileSync(path, "utf8")).accepted || []))
+      out[`${e.component}:${e.kind}:${e.prop ?? ""}`] = e.rationale || "accepted";
+    return out;
+  } catch { return {}; }
+}
+
+function classify(issues, component, accepted = {}) {
+  for (const i of issues) {
+    const key = `${component}:${i.kind}:${i.prop ?? ""}`;
+    if (accepted[key]) { i.severity = "info"; i.accepted = accepted[key]; }
+    else i.severity = ACTIONABLE.has(i.kind) ? "drift" : "info";
+  }
   return issues.some((i) => i.severity === "drift") ? "drift" : "ok";
 }
 
@@ -109,7 +140,7 @@ function likelyCounterpart(tag, byTag) {
   return hit || null;
 }
 
-export function componentDrift(contract, byTag) {
+export function componentDrift(contract, byTag, accepted = {}) {
   const tag = contract.tag;
   const el = byTag[tag];
 
@@ -118,7 +149,7 @@ export function componentDrift(contract, byTag) {
     if (alt) {
       const issues = [{ kind: "tag-mismatch", expected: tag, actual: alt,
         detail: `IR contract tag '${tag}' has no element; '${alt}' looks like the hand-authored counterpart (rename — resolve in Claude Design or realign the element).` }];
-      return { name: contract.name, status: classify(issues), tag, issues };
+      return { name: contract.name, status: classify(issues, contract.name, accepted), tag, issues };
     }
     return { name: contract.name, status: "new", tag, issues: [
       { kind: "no-counterpart", detail: `no <${tag}> in src/elements/ — stub generated.` },
@@ -127,6 +158,7 @@ export function componentDrift(contract, byTag) {
 
   const issues = [];
   const litProps = el.props;
+  const litSlots = el.slots || new Set();
   for (const p of contract.props || []) {
     if (p.portable === false) {
       issues.push({ kind: "non-portable", prop: p.name,
@@ -136,6 +168,13 @@ export function componentDrift(contract, byTag) {
     if (p.attribute === false) continue; // property-only by contract
     const lit = litProps[p.name];
     if (!lit) {
+      // A content prop can be honoured by a same-named named slot (e.g. PageHeader
+      // `actions` → <slot name="actions">) — that is satisfaction, not drift.
+      if (litSlots.has(p.name) || litSlots.has(p.attribute)) {
+        issues.push({ kind: "prop-via-slot", prop: p.name,
+          detail: `IR prop honoured by <slot name="${p.name}"> on <${tag}> (slotted content, not an attribute).` });
+        continue;
+      }
       issues.push({ kind: "prop-missing", prop: p.name,
         detail: `in IR (attribute '${p.attribute}'), absent on <${tag}>` });
       continue;
@@ -157,7 +196,7 @@ export function componentDrift(contract, byTag) {
       detail: `on <${tag}> (attribute '${litAttrOf(litProps[name]) ?? "(property-only)"}'), not in IR contract.` });
   }
 
-  return { name: contract.name, status: classify(issues), tag, issues };
+  return { name: contract.name, status: classify(issues, contract.name, accepted), tag, issues };
 }
 
 // ---------- Stub generation (write-once) ----------