fix(desktop): pass-2 correction C7 — degraded results observable + AppShell composite key

spawn_event_sync returns Result<(), String> so dispatch failure can be captured
by the workspace-apply post-commit section rather than being silently ignored.
The value is always Ok(()) since tauri::async_runtime::spawn is infallible; this
establishes the typed interface for future signaling.

try_regenerate_nest returns Result<(), String> instead of swallowing errors.
All fire-and-forget callers updated to .ok() to explicitly discard the Result.

apply_workspace post-commit:
- try_regenerate_nest moved out of the spawn_blocking closure into the async
  post-commit section so its Result can populate the degraded vec.
- spawn_event_sync Result captured; dispatch failure pushed to degraded.
- Nest failure reported as 'nest context regeneration failed: ...' degradation.

useCommunityInit.ts: post-commit degraded items now emit a toast.warning (8 s)
via sonner so the user sees partial failures. Previously only console.warn.

AppShell.tsx: useManagedAgentRuntimeReconciliation key changed from
String(reinitKey) to `${activeCommunity?.id}-${reinitKey}`. A same-relay
identity swap (new communityId, unchanged reinitKey) now correctly re-triggers
runtime reconciliation. Destructured activeCommunity and reinitKey from
communitiesHook and updated two other call sites for consistency.

dead pub use exports in migration.rs removed (fold, backfill, detach, strip,
materialize — all now accessed only through scoped _in_dir/_at variants).

Co-authored-by: Will Pfleger <pfleger.will@gmail.com>
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>

desktop/src/features/communities/useCommunityInit.ts

@@ -1,6 +1,7 @@
 import { useEffect, useRef, useState } from "react";
 import { isTauri } from "@tauri-apps/api/core";
 import { isMacPlatform } from "@/shared/lib/platform";
+import { toast } from "sonner";
 
 import { relayClient } from "@/shared/api/relayClient";
 import { resetRateLimitGate } from "@/shared/api/relayRateLimitGate";
@@ -238,13 +239,19 @@ export function useCommunityInit(
           return;
         }
 
-        // Workspace applied. Log any post-commit degradation (informational —
-        // the workspace IS active; these are best-effort post-commit steps).
+        // Workspace applied. Surface any post-commit degradation as a
+        // user-visible warning toast — the workspace IS active, but some
+        // best-effort post-commit steps failed (nest, event-sync, restore).
         if (applyResult.degraded.length > 0) {
+          const reason = applyResult.degraded.join("; ");
           console.warn(
             "[useCommunityInit] workspace applied with degradation:",
             applyResult.degraded,
           );
+          toast.warning("Workspace applied with partial failures", {
+            description: reason,
+            duration: 8000,
+          });
         }
       } catch (error) {
         // A bad `repos_dir` no longer reaches here — `apply_workspace` treats