feat(designbook): technology-neutral IR + stack-adapter pipeline (WHYNOT-WP-0002 T01-T06)

Author the design language once in the canonical React designbook and project it
one-way onto each stack: React -> designbook/ -> ir/ -> adapters/<stack>/.

Phase 0 — contracts & governance (T01-T03):
- ir/SCHEMA.md + ir/schema/{component,tokens}.schema.json — neutral IR contract
  (W3C DTCG tokens; React prop -> HTML attribute mapping; non-portable props flagged).
- adapters/ADAPTER_CONTRACT.md — inputs, drift-report + parity-result shapes,
  idempotency rules, CI exit codes (0 ok / 2 usage / 3 drift / 4 parity / 5 internal).
- .claude/rules/designbook-propagation.md + DesignSystemIntroduction.md §5.1 —
  one-way directionality + drift-resolution workflow.

T04 — canonical React designbook + the missing pull tool:
- The bundled /design-sync skill only PUSHES repo->cloud; it cannot populate
  designbook/. Added scripts/designbook_pull.py + `make designbook-pull`, which drives
  the local claude binary headless (acceptEdits) so DesignSync fetch+write runs in a
  subprocess (contents never hit the orchestrator's context). Pulled 44 files;
  excludes the _whynot-design-seed/ self-copy. Corrected the docs that wrongly called
  /design-sync the pull.

T05 — IR extractor (scripts/ir-extract.mjs + `make ir`):
- ir/tokens.json (80 tokens, DTCG, var() -> {ref} alias resolution); ir/components/*.json
  (10 contracts parsed from .jsx signatures: enum/boolean/number inference, prop->attr
  map, style/callback marked non-portable); ir/exemplars/*.

T06 — Lit token adapter (adapters/lit/ + `make adapt-lit`):
- Full-gen tokens into src/styles/colors_and_type.css :root (marker-bounded, idempotent
  no-op on re-run; hand-authored type CSS preserved).

NOTE: token regen synced Lit to canonical React — fonts IBM Plex -> system stacks and 8
status tokens added. This is a VISUAL change: review and run `pnpm test:visual:update`
before merge. Remaining: T07 scaffold+drift, T08 parity, T09 runbook, T10 2nd-adapter.

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

adapters/lit/README.md

@@ -0,0 +1,45 @@
+# Lit reference adapter
+
+Projects the technology-neutral IR (`ir/`) onto the Lit stack. This is the
+**reference** adapter — the contract every stack adapter implements lives in
+[`adapters/ADAPTER_CONTRACT.md`](../ADAPTER_CONTRACT.md).
+
+Run it with **`make adapt-lit`** (`adapters/lit/adapt.mjs`).
+
+## What it does
+
+Per the contract, an adapter is **scaffold + drift-detect**, never a rewrite:
+
+| Concern | Behaviour | Status |
+|---|---|---|
+| **Tokens** | **Fully generated** from `ir/tokens.json` into the `:root` block of `src/styles/colors_and_type.css`, between `@generated tokens` markers. Deterministic — re-running with an unchanged IR is a byte-identical no-op. The hand-authored type/utility CSS after the block is preserved. | **done (T06)** |
+| **New component** | Generate a `<wn-*>` Lit stub from the IR contract's prop→attribute map + a behaviour `TODO`. | T07 |
+| **Changed component** | Emit a **drift report** (`adapters/lit/drift/<Name>.md`) — never overwrite the hand-authored element. | T07 |
+
+## Directionality
+
+One-way: **React → `ir/` → Lit**. This adapter is downstream of the IR; it never
+writes back to `ir/` or to the React designbook. A change to the shared language is
+made in Claude Design and re-propagated (`make designbook-pull && make ir &&
+make adapt-lit`). See `.claude/rules/designbook-propagation.md`.
+
+## Token regeneration is a visual change
+
+Because tokens are fully generated, regenerating them can change rendered
+appearance when the canonical React designbook has moved (e.g. a font-stack or
+colour change). That makes the Playwright baselines diverge **by design** — it is a
+human review point, not an error:
+
+```
+make adapt-lit          # regenerates tokens
+pnpm test:visual        # will fail where appearance changed
+# review the change, then if correct:
+pnpm test:visual:update # accept new baselines
+```
+
+Never run `test:visual:update` to silence a token change without reviewing it — that
+defeats the parity gate (T08).
+
+## Exit codes
+
+`0` ok · `2` usage/config · `3` drift detected · `4` parity failure · `5` internal.

adapters/lit/adapt.mjs

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+#!/usr/bin/env node
+// =============================================================
+// adapters/lit/adapt.mjs — the Lit reference adapter (WHYNOT-WP-0002)
+//
+// Projects the technology-neutral IR (ir/) onto the Lit stack. Per
+// adapters/ADAPTER_CONTRACT.md this is scaffold + drift-detect, never a rewrite:
+//
+//   • tokens (T06)      → FULLY generated, deterministic (this file, today)
+//   • new component     → stub (T07)
+//   • changed component → drift report (T07), never an overwrite
+//
+// Exit codes: 0 ok · 2 usage/config · 3 drift · 4 parity · 5 internal.
+//
+// Run via `make adapt-lit`. Tokens regenerate the :root block of
+// src/styles/colors_and_type.css between generated markers; the hand-authored
+// type/utility CSS after it is preserved untouched. Re-running with an unchanged
+// ir/tokens.json is a no-op (byte-identical output).
+// =============================================================
+import { readFileSync, writeFileSync, existsSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const REPO = join(dirname(fileURLToPath(import.meta.url)), "..", "..");
+const TOKENS_JSON = join(REPO, "ir", "tokens.json");
+const TOKEN_CSS = join(REPO, "src", "styles", "colors_and_type.css");
+
+const BEGIN = "/* @generated tokens — regenerated by `make adapt-lit` from ir/tokens.json. DO NOT EDIT. */";
+const END = "/* @end generated tokens */";
+
+// ---------- tokens: ir/tokens.json (DTCG) → CSS custom properties ----------
+function refToVar(value) {
+  // {group.key} alias → var(--key). Literals pass through unchanged.
+  const m = /^\{[A-Za-z0-9]+\.([A-Za-z0-9-]+)\}$/.exec(String(value).trim());
+  return m ? `var(--${m[1]})` : value;
+}
+
+function renderRootBlock(tokens) {
+  const lines = [BEGIN, ":root {"];
+  for (const [group, entries] of Object.entries(tokens)) {
+    lines.push(`  /* ${group} */`);
+    for (const [key, tok] of Object.entries(entries)) {
+      if (key === "$type") continue;
+      lines.push(`  --${key}: ${refToVar(tok.$value)};`);
+    }
+  }
+  lines.push("}", END);
+  return lines.join("\n");
+}
+
+// Replace the current :root token region with the freshly generated block.
+// First run (no markers): replace the first `:root { … }` via brace matching.
+// Later runs: replace strictly between the @generated markers.
+function spliceTokenBlock(css, block) {
+  const b = css.indexOf(BEGIN);
+  if (b !== -1) {
+    const e = css.indexOf(END, b);
+    if (e === -1) throw new Error("Found @generated marker without its @end — refusing to guess.");
+    return css.slice(0, b) + block + css.slice(e + END.length);
+  }
+  const rootAt = css.indexOf(":root");
+  if (rootAt === -1) throw new Error("No :root block in colors_and_type.css to replace.");
+  let i = css.indexOf("{", rootAt), depth = 0;
+  for (; i < css.length; i++) {
+    if (css[i] === "{") depth++;
+    else if (css[i] === "}" && --depth === 0) break;
+  }
+  return css.slice(0, rootAt) + block + css.slice(i + 1);
+}
+
+function generateTokens() {
+  if (!existsSync(TOKENS_JSON)) {
+    console.error("No ir/tokens.json — run `make ir` first.");
+    process.exit(2);
+  }
+  const tokens = JSON.parse(readFileSync(TOKENS_JSON, "utf8"));
+  const block = renderRootBlock(tokens);
+  const before = existsSync(TOKEN_CSS) ? readFileSync(TOKEN_CSS, "utf8") : `${block}\n`;
+  const after = existsSync(TOKEN_CSS) ? spliceTokenBlock(before, block) : `${block}\n`;
+  const count = block.split("\n").filter((l) => l.trim().startsWith("--")).length;
+  if (after === before) {
+    console.log(`tokens: up to date (${count} custom properties, no change).`);
+    return;
+  }
+  writeFileSync(TOKEN_CSS, after);
+  console.log(`tokens: regenerated ${count} custom properties → src/styles/colors_and_type.css`);
+}
+
+function main() {
+  generateTokens();
+  // T07 will add: component stub scaffolding + drift reports here.
+  console.log("adapt-lit: tokens done. (component scaffold + drift: T07)");
+}
+
+main();