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>

CHANGELOG.md

@@ -21,6 +21,23 @@ Honest install badge — the flow list and analyzer only offer
 - **Analyzer not-in-store message** now names all three recovery
   paths instead of only the local-install hint (EN + DE).
 
+Project separation in the flow list:
+
+- **Workspace filter.** The file list filters by the host's
+  `activeProject`; flows without a `project:` key count as
+  `general` (display semantics — the file stays the truth and is
+  never rewritten). A project with no flows gets its own honest
+  empty state naming the project and the way out.
+- **New flows are stamped** with the active project's `project:`
+  key (`general` and "all projects" stay unstamped — no key
+  already means general).
+- **`toolbarTrailing` slot** on `FlowEditorPage`: the host can
+  place its workspace switcher in the editor's single toolbar.
+- **`flowsDir` injection** on `FlowEditorPage`: tests (and other
+  hosts) point the editor at any directory instead of the
+  hard-wired `~/.chain/data/flows` — the new widget tests run
+  against a temp dir, never the operator's flows.
+
 ## 0.24.1
 
 - No ALL-CAPS "FLOWS" panel header: the page toolbar already names