Don't reinstall sunshine when a working build is already present

Bug: install_sunshine always called yay_install on $SUNSHINE_PKG (default
sunshine-bin) before checking ldd. If the host already had sunshine (source
build) working, the bin install would replace it, trip the ldd check, and
the auto-recovery would rebuild source — a redundant 10-minute compile on
every ./install.sh re-run.

Fix: short-circuit at the top of install_sunshine when either sunshine or
sunshine-bin is already installed AND all its shared libs resolve. The
recovery dance only runs when there's actually something to fix.

lib/packages.sh

@@ -10,6 +10,21 @@
 install_sunshine() {
   # Ensure runtime deps useful for capture/diagnostics across vendors.
   yay_install pipewire-pulse vulkan-tools libva-utils jq
+
+  # If a working sunshine (source build) is already installed, don't touch it.
+  # Otherwise re-running install.sh would replace the source build with
+  # sunshine-bin (the default $SUNSHINE_PKG), trip the ldd check, then rebuild
+  # from source — a redundant ~10 minute compile on every re-run.
+  if pkg_installed sunshine && sunshine_runtime_deps_ok; then
+    ok "sunshine (source build) already installed with all shared libs resolved"
+    return 0
+  fi
+  # Same idempotency for sunshine-bin when it happens to be working.
+  if pkg_installed sunshine-bin && sunshine_runtime_deps_ok; then
+    ok "sunshine-bin already installed and runtime deps resolved"
+    return 0
+  fi
+
   yay_install "$SUNSHINE_PKG"
 
   # sunshine-bin is a precompiled AUR package; it breaks whenever Arch bumps a