feat(studio): Flows page IS the editor — three-tab graph+text+run

Studio's Flows destination is now the swappable
fai_studio_flow_editor's full surface: a drag-and-drop
graph view, the raw YAML text editor, and the run tab
with inputs form + live step progress + outputs.

What's gone:
 - The old saved-flows list + per-row run dialog.
 - The separate "flow-editor" navigation destination (one
   icon, not two — operators reach the editor by clicking
   Flows, period).
 - _FlowEditorAdapter (no longer needed; FlowsPage hands
   the runDriver to the editor directly).

What's new:
 - lib/data/flow_run_driver.dart — StudioFlowRunDriver:
   adapter implementing the editor's FlowRunDriver. Maps
   runFlow() to HubService.runSavedFlow and events() to
   HubService.streamEvents filtered to step.* event types.
   Converts proto-shaped FlowOutput variants to the editor's
   host-agnostic FlowOutputValue family.
 - lib/pages/flows.dart — replaced with a 50-line wrapper
   that loads capabilities into the editor's picker dropdown
   and forwards the active locale.

Editor pinned to fai_studio_flow_editor 0.2.0 (commit
870cbc2). All editor state — file list, dirty tracking, tab
selection, graph layout sidecar, properties panel — lives in
the editor package now; Studio just supplies the hub bridge.

Version 0.51.10 -> 0.52.0 (minor bump — Flows-page contract
changed, separate flow-editor destination removed).

flutter analyze: 0 issues. flutter test: 12/12 green.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

pubspec.lock

@@ -125,10 +125,10 @@ packages:
     description:
       path: "."
       ref: main
-      resolved-ref: daf6732893315c6841c4f32c69c19cd1dc3caca8
+      resolved-ref: "870cbc29f71a7fd9972755203714274ac128897b"
       url: "https://git.flemming.ai/fai/studio-flow-editor"
     source: git
-    version: "0.1.4"
+    version: "0.2.0"
   fake_async:
     dependency: transitive
     description: