build: Melos, a Dart check and every path for the single repository

- Melos 8.9 as the root's dev dependency, with scripts across the
  workspace (analyze, test:dart, test:flutter, generate, check) and its
  filters (--diff, --include-dependents); cli_util overridden to 0.5.2
  for it, since Learn's flutter_launcher_icons asks for 0.4 and uses only
  its logger, unchanged in 0.5.
- tool/check.dart in place of tool/check.sh: packages, formatting of our
  own files, analysis, the tools' tests, then every package's tests
  through Melos (--changed-since=<commit> for only what changed and what
  depends on it). tool/pre-push is the hook: the signature check, then
  the checks. CI generates every server's code and runs the same check.
- The images build from the root with a workspace narrowed to what they
  need (tool/workspace_only.sh); compose, the deploy's migration test,
  the snap, the release script, the editor's launch files and Learn's
  asset tools (run from apps/learn) follow the new layout.
- The project's source is named as project-halkyon/halkyon (source link,
  snap, F-Droid listing, release uploads); the AGPL packages carry the
  licence's own text.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

pubspec.yaml

@@ -27,10 +27,20 @@ workspace:
   - packages/halkyon_ui/example
 
 dev_dependencies:
+  # The tools' (tool/check.dart) options, and their tests (test/).
+  args: ^2.7.0
   # Referenced by analysis_options.yaml in this directory.
   leancode_lint: ^27.0.0
+  # Runs scripts across the workspace's packages (`melos:` below): `dart run melos …`.
+  melos: ^8.9.0
+  test: ^1.31.1
 
 dependency_overrides:
+  # Learn's flutter_launcher_icons (0.14.4, its latest, from June 2025) asks for
+  # cli_util ^0.4.1, Melos for 0.5 or later. Of cli_util it uses only the logger
+  # (`Logger.standard`, `Logger.verbose`, `Ansi`, `Progress`), the same in 0.5.2.
+  # Drop this once flutter_launcher_icons allows 0.5.
+  cli_util: ^0.5.2
   # The offline sync package's shared part from our fork: v0.0.10 with seven
   # changes. Byte payloads compared as bytes: v0.0.10 compares them byte by byte
   # through a UUID parse that throws for each byte, so a sync touching a few thousand
@@ -54,3 +64,43 @@ dependency_overrides:
       url: https://code.halkyon.app/project-halkyon/serverpod-offline-sync.git
       path: packages/serverpod_offline_sync
       ref: 949a6645e08af27bb61c96d7ddc2b6d145fed554
+
+# Melos (https://melos.invertase.dev): its scripts run across the workspace's packages,
+# `dart run melos run <name>`, and take Melos' filters, such as
+# `--diff=origin/main --include-dependents` for only what changed since main and what
+# depends on it. tool/check.dart runs the tests through them.
+melos:
+  scripts:
+    analyze:
+      description: Analyses the whole workspace, infos fatal too, as CI does.
+      run: dart analyze --fatal-infos
+    test:dart:
+      description: The tests of the packages without Flutter (servers, curator, the
+        shared Dart packages). Each server's start a PostgreSQL of their own on one
+        port, so one package at a time.
+      exec:
+        command: dart test
+        concurrency: 1
+      packageFilters:
+        flutter: false
+        dirExists: test
+    test:flutter:
+      description: The tests of the Flutter packages, those needing a running server
+        left out (`flutter test -t requires-server` runs them by hand).
+      exec:
+        command: flutter test -x requires-server
+        concurrency: 1
+      packageFilters:
+        flutter: true
+        dirExists: test
+    generate:
+      description: Serverpod's code generation in every server package (the CLI on
+        the PATH, at the version CI pins).
+      exec:
+        command: serverpod --no-analytics generate
+        concurrency: 1
+      packageFilters:
+        fileExists: config/generator.yaml
+    check:
+      description: Every check a push has to pass (tool/check.dart).
+      run: dart run tool/check.dart