feat(core-realtime): scaffold realtime optional core

Generator-emitted scaffold (pnpm turbo gen core-package realtime) plus
the story-00-precedent coverage repairs (coverage provider devDep,
symbols.ts exclude + tested allowlist mirror) and three minimal tests
covering generator-emitted realtime code the template suite misses.
Squash of 31d85e0 + review-fix cf11b38.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016j8z4VHjedXDTjEDNg7qHK

packages/core-eslint/rules/no-direct-socket-io.js

@@ -0,0 +1,39 @@
+// packages/core-eslint/rules/no-direct-socket-io.js
+const ALLOWED = [
+  /\/packages\/core-realtime\/src\//,
+  /\/apps\/[^/]+\/server\.ts$/,
+  /\/apps\/[^/]+\/src\/.*\.test\.ts$/,
+];
+
+export default {
+  meta: {
+    type: "problem",
+    docs: {
+      description:
+        "Block direct socket.io imports outside core-realtime + app servers",
+    },
+    messages: {
+      noDirectSocketIO:
+        'Import from "@repo/core-realtime" instead of "socket.io". Direct imports allowed only in packages/core-realtime/src/ and apps/*/server.ts.',
+      noDirectSocketIOClient:
+        'Use the realtime helpers from "@repo/core-realtime" / "@repo/core-testing/instrumentation" instead of "socket.io-client".',
+    },
+    schema: [],
+  },
+  create(context) {
+    const filename = context.filename ?? context.getFilename();
+    const allowed = ALLOWED.some((re) => re.test(filename));
+    if (allowed) return {};
+
+    return {
+      ImportDeclaration(node) {
+        const source = node.source.value;
+        if (source === "socket.io") {
+          context.report({ node, messageId: "noDirectSocketIO" });
+        } else if (source === "socket.io-client") {
+          context.report({ node, messageId: "noDirectSocketIOClient" });
+        }
+      },
+    };
+  },
+};

packages/core-eslint/rules/no-direct-socket-io.test.js

@@ -0,0 +1,48 @@
+// packages/core-eslint/rules/no-direct-socket-io.test.js
+import { RuleTester } from "eslint";
+import rule from "./no-direct-socket-io.js";
+
+const tester = new RuleTester({
+  languageOptions: { ecmaVersion: 2022, sourceType: "module" },
+});
+
+tester.run("no-direct-socket-io", rule, {
+  valid: [
+    // Allowed inside core-realtime
+    {
+      code: 'import { Server } from "socket.io";',
+      filename: "/repo/packages/core-realtime/src/socket-io-realtime-server.ts",
+    },
+    // Allowed in app servers
+    {
+      code: 'import { Server } from "socket.io";',
+      filename: "/repo/apps/web-next/server.ts",
+    },
+    // Allowed in app integration tests (e.g. realtime-ping e2e)
+    {
+      code: 'import { Server } from "socket.io";',
+      filename: "/repo/apps/web-next/src/__tests__/realtime-ping.test.ts",
+    },
+    {
+      code: 'import { io } from "socket.io-client";',
+      filename: "/repo/apps/web-next/src/__tests__/realtime-ping.test.ts",
+    },
+    // Allowed elsewhere when not importing socket.io
+    {
+      code: 'import { foo } from "bar";',
+      filename: "/repo/packages/blog/src/foo.ts",
+    },
+  ],
+  invalid: [
+    {
+      code: 'import { Server } from "socket.io";',
+      filename: "/repo/packages/blog/src/foo.ts",
+      errors: [{ messageId: "noDirectSocketIO" }],
+    },
+    {
+      code: 'import { io } from "socket.io-client";',
+      filename: "/repo/packages/blog/src/ui/Component.tsx",
+      errors: [{ messageId: "noDirectSocketIOClient" }],
+    },
+  ],
+});

packages/core-eslint/rules/no-realtime-handler-reexport.js

@@ -0,0 +1,48 @@
+// packages/core-eslint/rules/no-realtime-handler-reexport.js
+// Realtime handlers are private. A feature's realtime/handlers/*.handler.ts
+// must only be wired in the feature's own bind-production / bind-dev-seed files.
+// They must never be re-exported from barrel files or other public surfaces.
+
+const BIND_FILE = /\bdi\/bind-(?:production|dev-seed)\b/;
+const REALTIME_HANDLERS_IN_SOURCE = /\/realtime\/handlers\//;
+const HANDLERS_IN_SOURCE = /\/handlers\//;
+const REALTIME_IN_FILENAME = /\/realtime\//;
+
+export default {
+  meta: {
+    type: "problem",
+    docs: {
+      description:
+        "Block re-exports of realtime/handlers/** outside feature bind-* files (ADR-016 R1)",
+    },
+    messages: {
+      noRealtimeHandlerReexport:
+        "Realtime handlers (realtime/handlers/*.handler.ts) must not be re-exported (ADR-016 R1). " +
+        "Wire them only inside the feature's own bind-production / bind-dev-seed files.",
+    },
+    schema: [],
+  },
+  create(context) {
+    const filename = context.filename ?? context.getFilename();
+
+    // Bind-* files are the only allowed place for these exports/imports
+    if (BIND_FILE.test(filename)) return {};
+
+    function checkExportSource(node) {
+      if (!node.source) return;
+      const source = node.source.value;
+      const isRealtimeHandler =
+        REALTIME_HANDLERS_IN_SOURCE.test(source) ||
+        (HANDLERS_IN_SOURCE.test(source) &&
+          REALTIME_IN_FILENAME.test(filename));
+      if (isRealtimeHandler) {
+        context.report({ node, messageId: "noRealtimeHandlerReexport" });
+      }
+    }
+
+    return {
+      ExportNamedDeclaration: checkExportSource,
+      ExportAllDeclaration: checkExportSource,
+    };
+  },
+};

packages/core-eslint/rules/no-realtime-handler-reexport.test.js

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+// packages/core-eslint/rules/no-realtime-handler-reexport.test.js
+import { RuleTester } from "eslint";
+import rule from "./no-realtime-handler-reexport.js";
+
+const tester = new RuleTester({
+  languageOptions: { ecmaVersion: 2022, sourceType: "module" },
+});
+
+tester.run("no-realtime-handler-reexport", rule, {
+  valid: [
+    // Importing a handler from inside a feature's bind-* file is allowed.
+    {
+      code: 'import { onPingHandler } from "../realtime/handlers/on-ping.handler";',
+      filename: "/repo/packages/blog/src/di/bind-production.ts",
+    },
+    // Re-exporting a channel descriptor is allowed.
+    {
+      code: 'export { presenceChannel } from "./realtime/presence.channel";',
+      filename: "/repo/packages/blog/src/index.ts",
+    },
+  ],
+  invalid: [
+    // Re-exporting a handler from any non-bind file is forbidden.
+    {
+      code: 'export { onPingHandler } from "./realtime/handlers/on-ping.handler";',
+      filename: "/repo/packages/blog/src/index.ts",
+      errors: [{ messageId: "noRealtimeHandlerReexport" }],
+    },
+    {
+      code: 'export * from "./handlers/on-ping.handler";',
+      filename: "/repo/packages/blog/src/realtime/index.ts",
+      errors: [{ messageId: "noRealtimeHandlerReexport" }],
+    },
+  ],
+});