feat: Phase 0 workspace, spikes, and golden harness

Stand up the monorepo skeleton and land the first Phase 0 artifacts:
pairing threat model, plugin catalog, builder detect, 20-prompt golden
harness, and synthetic 2GB mirror timing.

e2e/golden/runs/latest.json

@@ -0,0 +1,130 @@
+{
+  "fixturePassed": 20,
+  "fixtureTotal": 20,
+  "grokLive": {
+    "skipped": true,
+    "reason": "XAI_API_KEY not set"
+  },
+  "scores": [
+    {
+      "id": "gb-01",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-02",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-03",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-04",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-05",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-06",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-07",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-08",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-09",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "gb-10",
+      "site": "gutenberg-business",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-01",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-02",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-03",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-04",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-05",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-06",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-07",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-08",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-09",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    },
+    {
+      "id": "el-10",
+      "site": "elementor-restaurant",
+      "passed": true,
+      "source": "fixture-tool-trace"
+    }
+  ]
+}

e2e/golden/runs/mirror-timing.json

@@ -0,0 +1,32 @@
+{
+  "blobBytes": 2147483648,
+  "runs": 20,
+  "subsetProxyMs": [
+    0.14750000000000796,
+    0.005541999999991276,
+    0.005167000000000144,
+    0.0027499999999918145,
+    0.009749999999996817,
+    0.0029590000000041528,
+    0.002415999999982432,
+    0.0023339999999905103,
+    0.0026249999999947704,
+    0.003458000000023276,
+    0.00566699999998832,
+    0.002916000000027452,
+    0.0017500000000154614,
+    0.0016249999999899956,
+    0.0016249999999899956,
+    0.0015829999999823485,
+    0.0014999999999929514,
+    0.0014999999999929514,
+    0.003500000000002501,
+    0.0015420000000005984
+  ],
+  "p50Ms": 0.0026249999999947704,
+  "p95Ms": 0.009749999999996817,
+  "uploadBytesCopied": 0,
+  "naiveCopyMs": 2449.693084,
+  "targetPageBudgetMs": 60000,
+  "decision": "slice holds"
+}