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>

CHANGELOG.md

@@ -4,6 +4,20 @@ All notable changes to `chain_studio_flow_editor` recorded here.
 Studio bumps its `pubspec.yaml` git ref to a specific release
 of this package on every editor change.
 
+## 0.22.0 — 2026-07-12
+
+### Added
+
+- **Project chip (multi-project stage ②).** When the open flow file
+  declares its own top-level `project:`, the editor shows it as a chip
+  in the tab action strip. If the file's project differs from the host's
+  active workspace, the chip becomes an amber "file wins" pill with a
+  one-click *Switch to <project>* action — the file always wins for the
+  run; switching only aligns the workspace view. New optional
+  `FlowEditorPage.activeProject` + `onSwitchToFileProject`; the parse +
+  normalize logic (mirrors the hub's `normalize_project_slug`) lives in
+  `flow_project.dart` and is unit-tested.
+
 ## 0.21.2 — 2026-07-11
 
 ### Added