feat: project chip + file-wins guard (multi-project stage 2)

When the open flow declares its own top-level project:, show it as a
chip in the tab action strip. On mismatch with the host's active
workspace, an amber file-wins pill offers a one-click Switch to
<project> — the file always wins for the run; switching only aligns
the workspace view.

New optional FlowEditorPage.activeProject + onSwitchToFileProject.
Parse + normalize (mirrors the hub's normalize_project_slug) lives in
flow_project.dart, unit-tested. flutter analyze clean, 57 tests green.

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

test/flow_project_test.dart

@@ -0,0 +1,47 @@
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:chain_studio_flow_editor/src/flow_project.dart';
+
+void main() {
+  group('parseFlowProject', () {
+    test('reads a bare top-level project key', () {
+      const yaml = 'name: demo\nproject: client-a\nsteps: []\n';
+      expect(parseFlowProject(yaml), 'client-a');
+    });
+
+    test('strips quotes and normalizes casing/spaces', () {
+      expect(parseFlowProject('project: "Client A"'), 'client-a');
+      // Non-[a-z0-9] that isn't a separator is dropped without a
+      // dash — matches the hub's normalize_project_slug.
+      expect(parseFlowProject("project: 'Recl∆Im'"), 'reclim');
+    });
+
+    test('returns empty when no top-level project is declared', () {
+      const yaml = 'name: demo\ninputs:\n  topic: text\nsteps: []\n';
+      expect(parseFlowProject(yaml), '');
+    });
+
+    test('ignores an indented project inside a step with-block', () {
+      const yaml =
+          'name: demo\nsteps:\n  - id: s\n    use: x@^0\n    with:\n      project: not-this\n';
+      expect(parseFlowProject(yaml), '');
+    });
+
+    test('a top-level project still wins over a later nested one', () {
+      const yaml =
+          'project: top\nsteps:\n  - id: s\n    with:\n      project: nested\n';
+      expect(parseFlowProject(yaml), 'top');
+    });
+  });
+
+  group('normalizeProjectSlug', () {
+    test('collapses separators and trims trailing dashes', () {
+      expect(normalizeProjectSlug('Projekt  Alpha__'), 'projekt-alpha');
+      expect(normalizeProjectSlug('a - b - c'), 'a-b-c');
+    });
+
+    test('empty stays empty', () {
+      expect(normalizeProjectSlug('   '), '');
+    });
+  });
+}