Remove the App Group wholesale — one sandbox, one bookmark, one flag

Phase 2 of the one-app pivot (DESIGN 12 ▸ App-side state, re-ruled
2026-07-30; reworks 566deab). AppGroup retires; what remains is
AppStateHome — ordinary sandbox Application Support as the one home for
the registry, clipboard staging and template stores, keeping the
unit-test-host redirect (the test host is the app and would sweep real
state). Scalar defaults return to UserDefaults.standard.

BoardRecord's per-edition grant slots and openNow flags collapse to one
bookmark + one isOpenNow; the legacy-key decode and adopt-in-memory
paths go (nothing shipped with group-era records), while the founding
four-keys-required / defaults-for-everything-since decode policy stays —
a bookmarkless record decodes as the born-orphan row rather than
quarantining the list. needsReopen and the pre-anchored re-grant panel
are removed whole: the only state that flow served — a record granted by
a sibling sandbox — is unrepresentable now, and a dead bookmark of our
own was already the orphan case by explicit comment. The
indexOfRecord path fallback dies with it; path is never a key again.

The cross-process freshness stamp (mtime+size re-read) and
BoardEditionPresence with its popover "Also open in…" line retire; the
clipboard prune keeps its atomic .sweeping/ claim-then-delete, reframed
for crash residue and open -n copies rather than sibling editions. The
application-groups entitlement key is gone.

1880 tests in 317 suites green (13 cross-edition tests retired with
their subject).

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

Kanban/KanbanApp.swift

@@ -54,7 +54,7 @@ struct KanbanApp: App {
 
         // Read first, because it decides *which app-side state the model is built over* — a fixture
         // launch keeps its recents and its clipboard snapshots in the scratch directory rather than in
-        // the shared App Group container.
+        // the app's ordinary Application Support home.
         let isUITestFixtureLaunch = UITestLaunch.isFixtureLaunch
         if isUITestFixtureLaunch {
             UITestLaunch.prepareScratchDirectory()
@@ -124,8 +124,7 @@ struct KanbanApp: App {
         // way to put a window on screen. Welcome's `.automatic` above is a request the system is free
         // to decline, and on macOS 26 it does: a launch with nothing to restore presented *no* scene
         // at all, which left `windowOpener` uncaptured and the app a windowless shell no menu action
-        // could revive (observed 2026-07-29; the per-edition open-now flags exposed it, because before
-        // them a flagged board almost always routed launches through this window). The pass itself
+        // could revive (observed 2026-07-29). The pass itself
         // still dispatches on the plan — a `.welcome` launch restores nothing and shows welcome —
         // and this window stays invisible and dismisses itself either way.
         .defaultLaunchBehavior(.presented)