T4: Per-app layout switching — focus watcher → layout push #10

Parent

#6

What to build

Connect the existing focus watcher to layout selection so the daemon automatically pushes the correct layout when the focused application changes. The daemon loads all YAML files from a layouts directory (not a single file), matches each focused app's AppInfo against the match list in each layout, and pushes the matching layout to all connected clients. Falls back to the default layout when no match is found.

Acceptance criteria

• Daemon accepts a --layouts-dir argument (or scans a layouts/ directory) and loads all YAML files at startup
• When the focused app changes, the daemon pushes the layout whose match list contains the app's app_id or wm_class
• When no layout matches, the daemon pushes the layout with match: [default]
• Switching between two apps that each have a layout pushes the correct layout each time
• FakeFocusBackend drives focus changes in tests; assertions verify correct LayoutMessage is pushed
• just watch-focus still works (focus backend unchanged)

Blocked by

• T1: Test foundation — pytest suite with fake sinks #7 (test foundation)