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/drift/_report.json

@@ -1,7 +1,7 @@
 {
   "stack": "lit",
-  "generatedAt": "2026-06-30T07:01:40.219Z",
-  "irRef": "17f2ad9",
+  "generatedAt": "2026-06-30T07:46:35.458Z",
+  "irRef": "756634c",
   "components": [
     {
       "name": "Button",
@@ -86,14 +86,14 @@
     },
     {
       "name": "PageHeader",
-      "status": "drift",
+      "status": "ok",
       "tag": "wn-page-header",
       "issues": [
         {
-          "kind": "prop-missing",
+          "kind": "prop-via-slot",
           "prop": "actions",
-          "detail": "in IR (attribute 'actions'), absent on <wn-page-header>",
-          "severity": "drift"
+          "detail": "IR prop honoured by <slot name=\"actions\"> on <wn-page-header> (slotted content, not an attribute).",
+          "severity": "info"
         },
         {
           "kind": "prop-extra",
@@ -105,28 +105,28 @@
     },
     {
       "name": "PipelineStrip",
-      "status": "drift",
-      "tag": "wn-pipeline-strip",
+      "status": "ok",
+      "tag": "wn-pipeline",
       "issues": [
         {
-          "kind": "tag-mismatch",
-          "expected": "wn-pipeline-strip",
-          "actual": "wn-pipeline",
-          "detail": "IR contract tag 'wn-pipeline-strip' has no element; 'wn-pipeline' looks like the hand-authored counterpart (rename — resolve in Claude Design or realign the element).",
-          "severity": "drift"
+          "kind": "prop-extra",
+          "prop": "stages",
+          "detail": "on <wn-pipeline> (attribute 'stages'), not in IR contract.",
+          "severity": "info"
         }
       ]
     },
     {
       "name": "Sidebar",
-      "status": "drift",
+      "status": "ok",
       "tag": "wn-sidebar",
       "issues": [
         {
           "kind": "prop-missing",
           "prop": "current",
           "detail": "in IR (attribute 'current'), absent on <wn-sidebar>",
-          "severity": "drift"
+          "severity": "info",
+          "accepted": "Composition divergence (intentional). The React Sidebar is monolithic and takes a `current` selection-key prop, comparing it against its own internal NAV_ITEMS. The Lit stack decomposes the sidebar into <wn-sidebar> + <wn-sidebar-group> + <wn-sidebar-item>, modelling selection as per-item `active` state on the slotted children rather than a container-level key. There is no single `current` attribute to honour on <wn-sidebar>; the contract is satisfied compositionally. Reconcile upstream only if the React designbook is ever made composable."
         },
         {
           "kind": "non-portable",
@@ -138,7 +138,8 @@
           "kind": "variant-axis-missing",
           "prop": "current",
           "detail": "IR variant axis 'current' (doc:) has no Lit property.",
-          "severity": "drift"
+          "severity": "info",
+          "accepted": "Same composition divergence as Sidebar.current above — the `current` variant axis is expressed as item-level `active` on <wn-sidebar-item>, not as a <wn-sidebar> property."
         },
         {
           "kind": "prop-extra",