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.

tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "experimentalDecorators": true,
+    "useDefineForClassFields": false,
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "esModuleInterop": true,
+    "verbatimModuleSyntax": true,
+    "paths": {}
+  },
+  "exclude": ["dist_*/**/*.d.ts"]
+}