feat(adapter): Lit component scaffold + drift report (WHYNOT-WP-0002 T07)

Extend make adapt-lit beyond tokens: parse src/elements/*.js, compare each IR
component contract against its <wn-*> element, and emit per-component drift
reports + a machine roll-up (adapters/lit/drift/), with write-once stubs
(adapters/lit/stubs/) for genuinely new components. Never overwrites
hand-authored sources.

- Severity split: actionable drift (prop-missing, attribute-mismatch,
  variant-axis-missing, tag-mismatch) gates with exit 3; non-portable + prop-extra
  are informational (the IR carries React style/onClick; Lit is richer than the
  minimal designbook) and don't gate.
- Current state: 7 ok, 3 actionable drift for human triage — PipelineStrip
  (wn-pipeline-strip vs hand-authored wn-pipeline rename), PageHeader (actions is
  a slot, not a prop), Sidebar (IR 'current' axis absent on the element).
- _report.json reuses generatedAt/irRef when drift is unchanged (no git churn).

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

adapters/lit/drift/PageHeader.md

@@ -0,0 +1,9 @@
+<!-- @generated by make adapt-lit (WHYNOT-WP-0002 T07) — overwritten each run; do not hand-edit. -->
+# Drift — PageHeader `<wn-page-header>`
+
+**Status:** drift — ⚠ drift detected — resolve per `.claude/rules/designbook-propagation.md`.
+
+| severity | kind | prop | detail |
+| --- | --- | --- | --- |
+| **drift** | prop-missing | `actions` | in IR (attribute 'actions'), absent on <wn-page-header> |
+| info | prop-extra | `hasActions` | on <wn-page-header> (attribute 'hasactions'), not in IR contract. |