Replace hand-written .d.ts with JSDoc + tsc auto-generation

- Delete hand-written index.d.ts that drifted from source
- Add JSDoc type annotations to all source files
- Create src/types.js with shared typedefs (SelfInfo, Contact,
  ContactMessage, ChannelInfo, RepeaterStats, etc.)
- Add tsconfig.json for declaration generation
- Add build:types script and prepublishOnly hook
- Add GitHub Actions CI workflow for type checking
- Use Uint8Array everywhere (no Buffer references)
- Add semantic type aliases (EpochSeconds, Milliseconds, MilliVolts)
- Add typed event overloads on Connection (on/once/off)
- All 11 PR #15 review comments addressed

package-lock.json

@@ -11,6 +11,10 @@
       "dependencies": {
         "@noble/curves": "^1.8.1",
         "serialport": "^13.0.0"
+      },
+      "devDependencies": {
+        "@types/node": "^25.2.3",
+        "typescript": "^5.9.3"
       }
     },
     "node_modules/@noble/curves": {
@@ -227,6 +231,16 @@
         "url": "https://opencollective.com/serialport/donate"
       }
     },
+    "node_modules/@types/node": {
+      "version": "25.2.3",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-25.2.3.tgz",
+      "integrity": "sha512-m0jEgYlYz+mDJZ2+F4v8D1AyQb+QzsNqRuI7xg1VQX/KlKS0qT9r1Mo16yo5F/MtifXFgaofIFsdFMox2SxIbQ==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "undici-types": "~7.16.0"
+      }
+    },
     "node_modules/debug": {
       "version": "4.4.0",
       "resolved": "https://registry.npmjs.org/debug/-/debug-4.4.0.tgz",
@@ -292,6 +306,27 @@
       "funding": {
         "url": "https://opencollective.com/serialport/donate"
       }
+    },
+    "node_modules/typescript": {
+      "version": "5.9.3",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-5.9.3.tgz",
+      "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "bin": {
+        "tsc": "bin/tsc",
+        "tsserver": "bin/tsserver"
+      },
+      "engines": {
+        "node": ">=14.17"
+      }
+    },
+    "node_modules/undici-types": {
+      "version": "7.16.0",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-7.16.0.tgz",
+      "integrity": "sha512-Zz+aZWSj8LE6zoxD+xrjh4VfkIG8Ya6LvYkZqtUQGJPZjYl53ypCaUwWqo7eI0x66KBGeRo+mlBEkMSeSZ38Nw==",
+      "dev": true,
+      "license": "MIT"
     }
   }
 }