feat(core-analytics): add IAnalytics interface, types, and NoopAnalytics

Replaces generator placeholder with IAnalytics interface (track, identify,
pageView, flush), AnalyticsAttributeValue + AnalyticsUser types, and
NoopAnalytics implementation. Adds sibling tests covering all four methods
with 100% coverage. All conformance + coverage gates pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

coverage/summary.json

@@ -1,18 +1,18 @@
 {
-  "generatedAt": "2026-05-13T18:36:10.133Z",
-  "commit": "9800fed",
+  "generatedAt": "2026-05-18T11:31:45.093Z",
+  "commit": "80c702e",
   "repo": {
-    "statements": 95.86,
-    "branches": 88.91,
+    "statements": 95.87,
+    "branches": 89.02,
     "functions": 100,
-    "lines": 95.86,
+    "lines": 95.87,
     "counts": {
-      "lf": 3113,
-      "lh": 2984,
-      "brf": 487,
-      "brh": 433,
-      "fnf": 142,
-      "fnh": 142
+      "lf": 3121,
+      "lh": 2992,
+      "brf": 492,
+      "brh": 438,
+      "fnf": 147,
+      "fnh": 147
     }
   },
   "byPackage": {
@@ -44,6 +44,20 @@
         "fnh": 29
       }
     },
+    "@repo/core-analytics": {
+      "statements": 100,
+      "branches": 100,
+      "functions": 100,
+      "lines": 100,
+      "counts": {
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+      }
+    },
     "@repo/marketing-pages": {
       "statements": 95.64,
       "branches": 83.93,