fix(release): use cargo-workspace + linked-versions plugins

.github/workflows/release-please-preview.yml

@@ -30,3 +30,14 @@ jobs:
     permissions:
       contents: read
       pull-requests: write
+    with:
+      # release-please-config.json has no "." package — it's a pure
+      # virtual cargo-workspace root split into per-member packages
+      # (core, app, tools/pack-cities, tools/pack-flags) linked by the
+      # linked-versions plugin with merge: true. Without this, forecast
+      # falls back to the manifest's first key, which happens to be
+      # right here (every linked package shares one version) but leaves
+      # it guessing rather than told — naming "core" explicitly is what
+      # silences that preflight warning. See non7top/release-please-forecast's
+      # README "Multi-package repositories" section.
+      package-name: core

.release-please-manifest.json

@@ -1,3 +1,6 @@
 {
-  ".": "0.1.0"
+  "core": "0.1.0",
+  "app": "0.1.0",
+  "tools/pack-cities": "0.1.0",
+  "tools/pack-flags": "0.1.0"
 }

release-please-config.json

@@ -1,11 +1,20 @@
 {
   "$schema": "https://raw.githubusercontent.com/googleapis/release-please/main/schemas/config.json",
-  "packages": {
-    ".": {
-      "release-type": "rust",
-      "changelog-path": "CHANGELOG.md",
-      "include-component-in-tag": false,
-      "extra-label": "RELEASE"
+  "include-component-in-tag": false,
+  "extra-label": "RELEASE",
+  "plugins": [
+    { "type": "cargo-workspace", "merge": false },
+    {
+      "type": "linked-versions",
+      "groupName": "sort4print",
+      "components": ["sort4print-core", "sort4print", "pack-cities", "pack-flags"],
+      "merge": true
     }
+  ],
+  "packages": {
+    "core": { "release-type": "rust", "component": "sort4print-core" },
+    "app": { "release-type": "rust", "component": "sort4print" },
+    "tools/pack-cities": { "release-type": "rust", "component": "pack-cities" },
+    "tools/pack-flags": { "release-type": "rust", "component": "pack-flags" }
   }
 }