FN-6106: block plugin view re-exports from server entries

Add an ESLint guard to keep plugin dashboard views out of server entrypoints.

- add a custom fusion/no-plugin-view-reexport ESLint rule for plugin src/index.ts files
- flag relative re-exports of *-view entrypoints so CSS-bearing dashboard modules stay out of Node-loaded plugin entries
- document the server-entry export constraint in the plugin authoring guide

Files changed:
 docs/PLUGIN_AUTHORING.md |  1 +
 eslint.config.mjs        | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

Fusion-Task-Id: FN-6106

Fusion-Task-Lineage: 6bbfa073-e7fd-42a9-a332-c638b81cd55f

docs/PLUGIN_AUTHORING.md

@@ -763,6 +763,7 @@ The host then renders plugin views via `PluginDashboardViewHost` using the compo
 Bundled workspace plugin pattern:
 - Keep plugin package under `plugins/` (for example `plugins/fusion-plugin-roadmap`)
 - Export backend/plugin entry from `src/index.ts` and keep dashboard view exports in the plugin package (for example `./dashboard-view`)
+- Do not re-export dashboard view entrypoints (including `dashboard-view`, `manage-view`, or other `-view` modules) from `src/index.ts`; the `fusion/no-plugin-view-reexport` ESLint guard catches violations because server-side plugin entries must not transitively load CSS
 - Register the lazy dashboard component in host code (currently `packages/dashboard/app/plugins/registerBundledPluginViews.ts`)
 - CLI bundling inlines backend plugin code from workspace packages; dashboard view modules are imported by the dashboard build via the host registry
 

eslint.config.mjs

@@ -69,6 +69,36 @@ const detachedSpawnGuard = {
   },
 };
 
+const noPluginViewReexport = {
+  meta: {
+    type: "problem",
+    docs: {
+      description: "ban dashboard view re-exports from plugin server entry points",
+    },
+    schema: [],
+  },
+  create(context) {
+    function isViewEntrypointReexportSource(value) {
+      return typeof value === "string"
+        && value.startsWith(".")
+        && /(?:^|\/)[^/]*-view(?:\.(?:js|tsx))?$/.test(value);
+    }
+
+    return {
+      ExportNamedDeclaration(node) {
+        if (!isViewEntrypointReexportSource(node.source?.value)) {
+          return;
+        }
+        context.report({
+          node: node.source,
+          message:
+            "Plugin server entry (src/index.ts) must not re-export dashboard view components. Use a dedicated subpath export (e.g. './dashboard-view') instead — see docs/PLUGIN_AUTHORING.md.",
+        });
+      },
+    };
+  },
+};
+
 /**
  * ESLint Flat Config for Fusion Workspace
  * 
@@ -339,6 +369,23 @@ export default tseslint.config(
     },
   },
 
+  // ─────────────────────────────────────────────────────────────
+  // PLUGIN SERVER ENTRYPOINTS — keep dashboard views out of Node-loaded entries
+  // ─────────────────────────────────────────────────────────────
+  {
+    files: ["plugins/**/src/index.ts", "plugins/examples/**/src/index.ts"],
+    plugins: {
+      fusion: {
+        rules: {
+          "no-plugin-view-reexport": noPluginViewReexport,
+        },
+      },
+    },
+    rules: {
+      "fusion/no-plugin-view-reexport": "error",
+    },
+  },
+
   // ─────────────────────────────────────────────────────────────
   // AGENT SKILL TEMPLATES — template code with underscore prefix support
   // (agent prompt templates use _prefixed placeholders intentionally)