feat(FN-1469): create settings-loadable example plugin

- Add fusion-plugin-settings-demo package with settings schema (string, number, boolean, enum types)
- Add lifecycle hooks (onLoad, onTaskCreated, onTaskCompleted)
- Add tools (suggest_tags, status) with settings-driven behavior
- Add comprehensive tests with 24 test cases
- Add manifest.json for plugin metadata and README with Settings installation flow
- Update PLUGIN_AUTHORING.md with new example and install instructions
- Also includes: FN-1468 plugin wiring, FN-1456 abandon flow, FN-1429 always-green tests, FN-1440 Authentication in Settings, FN-1133 plugin hot-reload support

plugins/examples/fusion-plugin-settings-demo/package.json

@@ -0,0 +1,27 @@
+{
+  "name": "@fusion-plugin-examples/settings-demo",
+  "version": "0.1.0",
+  "type": "module",
+  "description": "Example Fusion plugin demonstrating settings schema and runtime configuration",
+  "keywords": [
+    "fusion-plugin"
+  ],
+  "exports": {
+    ".": {
+      "types": "./src/index.ts",
+      "import": "./src/index.ts"
+    }
+  },
+  "private": true,
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run"
+  },
+  "dependencies": {
+    "@fusion/plugin-sdk": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/node": "^25.5.2",
+    "vitest": "^3.2.4"
+  }
+}