feat(plugins): core read-only scripts and user plugin system

Introduce plugin/<id> installs (zip, HTTPS git, example, fork),
jerapah-plugin.json manifests with jerapah semver ranges, isolated
plugin dirs under data/plugins, and app version 0.1.0. Core scripts
are non-editable; get-current-time moves to examples/plugins.

Co-authored-by: Nasyarobby Putra <nasyarobby@gmail.com>

examples/plugins/get-current-time/jerapah-plugin.json

@@ -0,0 +1,8 @@
+{
+  "id": "get-current-time",
+  "name": "Get current time",
+  "version": "0.1.0",
+  "jerapah": ">=0.1.0 <1.0.0",
+  "main": "script.js",
+  "description": "Example user plugin: return the current time as output.datetime"
+}

examples/plugins/get-current-time/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "jflow-plugin-get-current-time",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "description": "Example JerapahFlow plugin (no npm dependencies)"
+}

examples/plugins/get-current-time/script.js

@@ -0,0 +1,34 @@
+function passContext(ctx) {
+  if (ctx?.context != null && typeof ctx.context === "object" && !Array.isArray(ctx.context)) {
+    return { ...ctx.context };
+  }
+  return {};
+}
+
+function getCurrentTime(ctx) {
+  const output = {
+    datetime: new Date().toISOString(),
+    processId: "1234",
+  };
+  return { output, context: { ...passContext(ctx), ...output } };
+}
+
+getCurrentTime.meta = {
+  description: "Return the current time as output.datetime",
+  config: {},
+  input: {},
+  output: {
+    datetime: { type: "string", description: "ISO timestamp" },
+    processId: { type: "string" },
+  },
+  context: {
+    datetime: { type: "string", description: "ISO timestamp" },
+    processId: { type: "string" },
+  },
+  example: {
+    data: {},
+    config: {},
+  },
+};
+
+export default getCurrentTime;