feat: project separation in the flow list (0.25.0)

Filter the file list by the host's active project — flows without
a project: key count as 'general', display-only, the file is never
rewritten. New flows are stamped with the active project's key
(general and all-projects stay unstamped). Adds a toolbarTrailing
slot so the host can mount its workspace switcher in the editor's
single toolbar, and a flowsDir injection point so widget tests run
against a temp dir instead of the operator's ~/.chain flows.
Covered by pure filter-semantics tests plus hermetic widget tests
for filtering, the project-empty state, and new-flow stamping.

Signed-off-by: flemming-it <sf@flemming.it>

lib/src/flow_editor_page.dart

@@ -120,6 +120,18 @@ class FlowEditorPage extends StatefulWidget {
   /// (the mismatch note still shows — the file still wins).
   final void Function(String fileProject)? onSwitchToFileProject;
 
+  /// Host-injected widget rendered in the editor toolbar, before
+  /// the New-flow button. Studio places its workspace (project)
+  /// switcher here — the editor keeps a single toolbar and stays
+  /// host-agnostic.
+  final Widget? toolbarTrailing;
+
+  /// Directory the editor lists/saves flow files in. `null` uses
+  /// the hub's default (`~/.chain/data/flows`). Tests inject a
+  /// temp dir so they never touch the operator's real flows
+  /// (hermetic per shared/TESTING.md).
+  final String? flowsDir;
+
   const FlowEditorPage({
     super.key,
     this.initialFlowName,
@@ -133,6 +145,8 @@ class FlowEditorPage extends StatefulWidget {
     this.activeProject = '',
     this.onSwitchToFileProject,
     this.onPickFile,
+    this.toolbarTrailing,
+    this.flowsDir,
   });
 
   @override
@@ -293,8 +307,10 @@ class _FlowEditorPageState extends State<FlowEditorPage>
 
   // --- file ops ---
 
+  String get _flowsDir => widget.flowsDir ?? _defaultFlowsDir();
+
   Future<List<_FlowFile>> _listFiles() async {
-    final dir = Directory(_defaultFlowsDir());
+    final dir = Directory(_flowsDir);
     if (!dir.existsSync()) return <_FlowFile>[];
     final entries = await dir
         .list()
@@ -333,7 +349,7 @@ class _FlowEditorPageState extends State<FlowEditorPage>
   }
 
   Future<void> _openByName(String name) async {
-    final path = '${_defaultFlowsDir()}/$name.yaml';
+    final path = '$_flowsDir/$name.yaml';
     final file = File(path);
     if (!file.existsSync()) return;
     final text = await file.readAsString();
@@ -376,7 +392,7 @@ class _FlowEditorPageState extends State<FlowEditorPage>
     if (name == null) return;
     _controller.saving = true;
     try {
-      final file = File('${_defaultFlowsDir()}/$name.yaml');
+      final file = File('$_flowsDir/$name.yaml');
       await file.writeAsString(
         _controller.codeController.fullText,
         flush: true,
@@ -420,11 +436,18 @@ class _FlowEditorPageState extends State<FlowEditorPage>
       builder: (ctx) => _NewFlowDialog(strings: _l),
     );
     if (name == null || name.isEmpty || !mounted) return;
+    // Stamp the active workspace project into the new file so the
+    // flow stays visible under the filter it was created in. The
+    // file wins from here on; `general` (and "all projects") stay
+    // unstamped — no key already means general.
+    final project = widget.activeProject;
+    final projectLine =
+        project.isEmpty || project == 'general' ? '' : 'project: $project\n';
     final template =
         '''# ${_l.newTemplateComment(name)}
 
 name: $name
-
+$projectLine
 inputs:
   text:
     type: text
@@ -439,7 +462,7 @@ outputs:
   result: \$echo.echoed
 ''';
     try {
-      final dir = Directory(_defaultFlowsDir());
+      final dir = Directory(_flowsDir);
       if (!dir.existsSync()) await dir.create(recursive: true);
       final file = File('${dir.path}/$name.yaml');
       if (file.existsSync()) {
@@ -577,6 +600,7 @@ outputs:
                 ? () => Navigator.of(context).maybePop()
                 : null,
             onNew: _newFlow,
+            trailing: widget.toolbarTrailing,
           ),
           const Divider(height: 1),
           Expanded(
@@ -593,6 +617,7 @@ outputs:
                       widget.availableCapabilities,
                     ),
                     storeNames: _installedNames(widget.storeCapabilities),
+                    activeProject: widget.activeProject,
                     onOpen: _openFile,
                     onRefresh: _refreshFiles,
                     onStart: _startFile,
@@ -946,12 +971,18 @@ class _Toolbar extends StatelessWidget {
   final bool dirty;
   final VoidCallback? onBack;
   final VoidCallback onNew;
+
+  /// Host-injected widget rendered before the New-flow button —
+  /// Studio places its workspace (project) switcher here so the
+  /// editor keeps a single toolbar and stays host-agnostic.
+  final Widget? trailing;
   const _Toolbar({
     required this.strings,
     required this.activeName,
     required this.dirty,
     required this.onBack,
     required this.onNew,
+    this.trailing,
   });
 
   @override
@@ -1020,6 +1051,10 @@ class _Toolbar extends StatelessWidget {
             ),
           ],
           const Spacer(),
+          if (trailing != null) ...[
+            trailing!,
+            const SizedBox(width: FaiSpace.md),
+          ],
           FilledButton.tonalIcon(
             onPressed: onNew,
             icon: const Icon(Icons.add, size: 16),
@@ -1257,7 +1292,16 @@ const String _sampleFlowMarker = 'F∆I sample flow';
 class _FlowMeta {
   final bool isExample;
   final List<String> requiredCaps;
-  const _FlowMeta({required this.isExample, required this.requiredCaps});
+
+  /// The file's own normalized `project:` slug; empty when the
+  /// YAML declares none (which counts as `general` for the list
+  /// filter — display semantics only, the file is never rewritten).
+  final String project;
+  const _FlowMeta({
+    required this.isExample,
+    required this.requiredCaps,
+    this.project = '',
+  });
 
   static const empty = _FlowMeta(isExample: false, requiredCaps: []);
 
@@ -1321,7 +1365,11 @@ _FlowMeta _scanFlow(String text) {
     final name = value.split('@').first.trim();
     if (name.isNotEmpty) caps.add(name);
   }
-  return _FlowMeta(isExample: isExample, requiredCaps: caps.toList());
+  return _FlowMeta(
+    isExample: isExample,
+    requiredCaps: caps.toList(),
+    project: parseFlowProject(text),
+  );
 }
 
 /// Reduce the host-supplied installed list (entries like
@@ -1355,6 +1403,10 @@ class _FileList extends StatefulWidget {
   /// outside this set render the "not in store" state instead
   /// of an install action that the hub would refuse.
   final Set<String> storeNames;
+
+  /// Active workspace project slug; empty = all projects. Files
+  /// without a `project:` key count as `general`.
+  final String activeProject;
   final void Function(_FlowFile) onOpen;
   final VoidCallback onRefresh;
 
@@ -1374,6 +1426,7 @@ class _FileList extends StatefulWidget {
     required this.strings,
     required this.installedNames,
     required this.storeNames,
+    required this.activeProject,
     required this.onOpen,
     required this.onRefresh,
     required this.onStart,
@@ -1488,10 +1541,35 @@ class _FileListState extends State<_FileList> {
             ),
           );
         }
+        // Workspace filter first: files without a `project:` key
+        // count as `general` (display semantics — the file is the
+        // truth and never rewritten).
+        final inProject = all
+            .where(
+              (f) => flowVisibleInProject(
+                f.meta.project,
+                widget.activeProject,
+              ),
+            )
+            .toList();
+        if (inProject.isEmpty) {
+          // Flows exist, just none in this project — say that and
+          // point at the way out (switch to all projects).
+          return Padding(
+            padding: const EdgeInsets.all(FaiSpace.md),
+            child: FaiEmptyState(
+              icon: Icons.folder_off_outlined,
+              title: strings.listProjectEmpty(widget.activeProject),
+              hint: strings.listProjectEmptyHint,
+            ),
+          );
+        }
         final needle = _filter.toLowerCase();
         final files = needle.isEmpty
-            ? all
-            : all.where((f) => f.name.toLowerCase().contains(needle)).toList();
+            ? inProject
+            : inProject
+                  .where((f) => f.name.toLowerCase().contains(needle))
+                  .toList();
         if (files.isEmpty) {
           // Flows exist, the filter just matches none — say that
           // instead of pretending the directory is empty.

lib/src/flow_project.dart

@@ -24,6 +24,21 @@ String parseFlowProject(String yaml) {
   return '';
 }
 
+/// The project a flow file effectively belongs to: its own
+/// `project:` slug, or `general` when the file declares none.
+/// Display/filter semantics only — the FILE stays the truth and
+/// is never rewritten to make this explicit.
+String effectiveFlowProject(String fileProject) =>
+    fileProject.isEmpty ? 'general' : fileProject;
+
+/// Whether a flow file belongs in the list under the active
+/// workspace filter. Empty [activeProject] = "all projects";
+/// otherwise the file's effective project (no key = `general`)
+/// must match.
+bool flowVisibleInProject(String fileProject, String activeProject) =>
+    activeProject.isEmpty ||
+    effectiveFlowProject(fileProject) == activeProject;
+
 /// Mirror of the hub's `normalize_project_slug`: lowercase,
 /// collapse spaces/underscores/dashes to a single `-`, drop
 /// everything else, trim trailing dashes. Empty in → empty out

lib/src/l10n.dart

@@ -314,6 +314,19 @@ class FlowEditorStrings {
             '(MCP/n8n) einrichten, die die Capability bereitstellt.',
       );
 
+  // Project-scoped empty state: flows exist, none in the active
+  // workspace project.
+  String listProjectEmpty(String project) => _t(
+        'No flows in project "$project".',
+        'Keine Flows im Projekt „$project".',
+      );
+  String get listProjectEmptyHint => _t(
+        'New flow puts one here, or switch the project selector to '
+            '"All projects".',
+        '„Neuer Flow" legt hier einen an — oder wechseln Sie die '
+            'Projekt-Auswahl auf „Alle Projekte".',
+      );
+
   // Flow-list filter (first iteration: plain substring match).
   String get listFilterHint => _t('Filter flows…', 'Flows filtern…');
   String listFilterNoMatch(String query) => _t(