feat(core): initial release with 3-tier secret storage

Implements SmartSecret with macOS Keychain, Linux secret-tool, and AES-256-GCM encrypted file fallback backends. Zero runtime dependencies.

npmextra.json

@@ -0,0 +1,28 @@
+{
+  "npmci": {
+    "npmAccessLevel": "public"
+  },
+  "gitzone": {
+    "projectType": "npm",
+    "module": {
+      "githost": "code.foss.global",
+      "gitscope": "push.rocks",
+      "gitrepo": "smartsecret",
+      "description": "OS keychain-based secret storage with encrypted-file fallback for Node.js.",
+      "npmPackagename": "@push.rocks/smartsecret",
+      "license": "MIT",
+      "keywords": [
+        "secret",
+        "keychain",
+        "credential",
+        "vault",
+        "encryption",
+        "security",
+        "keyring",
+        "libsecret",
+        "macos-keychain",
+        "aes-256-gcm"
+      ]
+    }
+  }
+}