fix(desktop): recover chat after sleep/wake by revalidating a stale remote backend

After sleep/wake, a remote (global-remote) primary backend can become
unreachable, but it has no child process whose 'exit' clears the main
process's cached connectionPromise. The renderer then re-dials the same
dead remote forever and the composer stays stuck on "Starting Hermes…";
only a quit+reopen recovered.

Fix: the renderer's existing backoff-paced reconnect loop now asks the
main process to revalidate the cached connection before re-dialing. The
main process liveness-probes the cached REMOTE backend's public
/api/status and, if unreachable, drops the cache (resetHermesConnection
only nulls connectionPromise for a remote — no child to SIGTERM) so the
next getConnection() rebuilds a reachable descriptor. Local backends are
never touched here; they self-heal via the child 'exit' handler. The
renderer's loop already provides retry pacing and rides out transient
blips, so no streak/episode bookkeeping is needed in the main process.

The boot hook dismisses the boot-progress overlay on the post-rebuild
'open' so an in-place rebuild can't leave it stuck at ~94%.

Reimplements #40135 by @AlchemistChaos on a smaller, more interpretable
path (63 added lines vs 555): no extracted helper module, no
failure-streak / episode-window state, the renderer's backoff loop is
the retry mechanism. Original diagnosis and fix by @AlchemistChaos.

Co-authored-by: AlchemistChaos <alchemistchaos@protonmail.com>

apps/desktop/src/app/gateway/hooks/use-gateway-boot.ts

@@ -120,6 +120,13 @@ export function useGatewayBoot({
       reconnecting = true
 
       try {
+        // Drop a stale REMOTE backend cache before re-dialing. After sleep/wake a
+        // remote backend can become unreachable, but it has no child process
+        // whose 'exit' would clear the main process's cached descriptor — without
+        // this the renderer re-dials the same dead endpoint forever and stays on
+        // "Starting Hermes…". The probe is a no-op for a healthy or local backend.
+        await desktop.revalidateConnection?.().catch(() => undefined)
+
         const conn = await desktop.getConnection($activeGatewayProfile.get())
 
         if (cancelled) {
@@ -218,6 +225,15 @@ export function useGatewayBoot({
         reconnectAttempt = 0
         reauthNotified = false
         clearReconnectTimer()
+
+        // A revalidate-driven reconnect can rebuild the backend in place when the
+        // cached remote was found dead, which re-drives the boot-progress overlay.
+        // Unlike the initial boot, nothing calls completeDesktopBoot() afterwards,
+        // so dismiss it here once we're open again — otherwise the overlay sticks
+        // at ~94%. A no-op on a normal (non-rebuild) reconnect.
+        if (bootCompleted) {
+          completeDesktopBoot()
+        }
       } else if (bootCompleted && (st === 'closed' || st === 'error')) {
         // The socket dropped after a healthy boot (typically sleep/wake). Try
         // to bring it back instead of leaving the composer stuck disabled.

apps/desktop/src/global.d.ts

@@ -7,6 +7,13 @@ declare global {
       // the window's backend; pass a named profile to lazily spawn/reuse that
       // profile's backend from the pool.
       getConnection: (profile?: string | null) => Promise<HermesConnection>
+      // Reconnect-after-wake recovery: liveness-probe the cached PRIMARY backend
+      // and drop it if a remote one has gone unreachable, so the next
+      // getConnection() rebuilds a reachable descriptor instead of the renderer
+      // re-dialing a dead remote forever. No-op for local backends (they
+      // self-heal via the child 'exit' handler). `rebuilt` is true when a stale
+      // remote cache was dropped.
+      revalidateConnection: () => Promise<{ ok: boolean; rebuilt: boolean }>
       // Keepalive: mark a pool profile backend as recently used so the idle
       // reaper spares it while its chat is active.
       touchBackend: (profile?: string | null) => Promise<{ ok: boolean }>