fix(daemon): never restart, delete or swap under a node that hasn't exited

Every operation that stops the node (restart, rescan, repair, delete
chain data, reinstall, bootstrap, wallet switch/adopt/restore/rebuild,
wizard restart, encrypt, decrypt) now:

- refuses up front while the node is rebuilding witnesses or has not
  answered for 30s, with a "try again when it's done" warning, and sends
  no stop;
- goes ahead only once the node's PROCESS has exited, not its RPC port.
  A stop that doesn't finish within 120s cancels the operation (warning;
  a cancelled rescan/repair disarms its flags); nothing is started over
  the old node, chain data isn't deleted, wallet.dat isn't swapped.

Specifics:
- stopDaemonForWalletSwitch() no longer reports "stopped" when the app
  is quitting (adopt could swap wallet.dat under a live node).
- Decrypt waited a fixed 3s after "stop" before renaming wallet.dat; it
  now waits for the process to exit, and scrubs the key export if not.
- Bootstrap waits for the process before cleanChainData and stops the
  node through the stop routine instead of the shared RPC client.
- StopScope::Connected lets switch/reinstall/decrypt stop an adopted or
  external node through the same never-kill routine.
- A bounded stop that can't reach the node (a foreign node refusing our
  credentials) gives up after 5s instead of 120s.
- macOS: isDaemonProcessRunning() checks processes (libproc), not the
  RPC port.
- rpcBusyWhileAlive() also reads the busy gate: since the gate, the
  first timeout usually lands on another lane and the 30s clock never
  started (also weakened the quit prompt for a silent rebuild).
- Notifications render during the first-run wizard.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/services/wallet_security_workflow_executor.cpp

@@ -64,8 +64,10 @@ WalletSecurityWorkflowExecutor::Outcome WalletSecurityWorkflowExecutor::restartD
     if (!waitForMs(preRestartDelayMs)) return {false, "", false};
 
     if (daemon.isUsingEmbeddedDaemon()) {
-        daemon.stopEmbeddedDaemon();
+        const bool stopped = daemon.stopEmbeddedDaemon();
         if (daemon.cancelled() || daemon.shuttingDown()) return {false, "", false};
+        // Never start a second node over one that hasn't exited (it holds wallet.dat and the datadir lock).
+        if (!stopped) return {false, "The node did not stop in time, so it was not restarted.", false};
         if (!waitForMs(embeddedRestartSettleMs)) return {false, "", false};
         daemon.startEmbeddedDaemon();
     }

src/services/wallet_security_workflow_executor.h

@@ -49,7 +49,7 @@ public:
     public:
         virtual ~DaemonGateway() = default;
         virtual bool isUsingEmbeddedDaemon() const = 0;
-        virtual void stopEmbeddedDaemon() = 0;
+        virtual bool stopEmbeddedDaemon() = 0;   // true: the node exited (false: still running; never killed)
         virtual bool startEmbeddedDaemon() = 0;
         virtual bool cancelled() const = 0;
         virtual bool shuttingDown() const = 0;