chore(packaging): CI + package guards for the Linux frame-copy helper

- build-and-make.yaml: install libegl-dev/libgl-dev/libgbm-dev on the
  Linux runner (the helper's EGL backend needs them now that the helper
  target builds on Linux), and verify the built helper exists and DOES
  link libmpv - the inverse of the addon's no-libmpv rule, which still
  holds and stays validated.
- electron-after-pack.cjs: strip iptvnator_mpv_helper from packaged Linux
  apps. It links the build host's system libmpv, which end-user systems
  cannot be assumed to have; the support probe treats the missing helper
  as frame-copy-unavailable (dev-build-only engine until the
  bundled-runtime staging milestone).
- frame_helper_gl.h: log the chosen EGL display tier to stderr (the
  adapter mirrors helper stderr), so bring-up problems on exotic setups
  are diagnosable.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/build-and-make.yaml

@@ -68,7 +68,7 @@ jobs:
               if: matrix.os == 'linux'
               run: |
                   sudo apt-get update
-                  sudo apt-get install --no-install-recommends -y rpm libarchive-tools flatpak flatpak-builder appstream libx11-dev libxext-dev libmpv-dev mpv pkg-config
+                  sudo apt-get install --no-install-recommends -y rpm libarchive-tools flatpak flatpak-builder appstream libx11-dev libxext-dev libmpv-dev mpv pkg-config libegl-dev libgl-dev libgbm-dev
 
                   # Configure Flatpak
                   # 1. Add the Flathub repository (source of runtimes)
@@ -336,6 +336,15 @@ jobs:
                           ldd dist/apps/electron-backend/native/embedded_mpv.node
                           exit 1
                       fi
+                      # The frame-copy helper is the inverse: a separate process
+                      # that MUST link libmpv (dev-mode engine; stripped from
+                      # packages until the bundled-runtime staging lands).
+                      test -x dist/apps/electron-backend/native/iptvnator_mpv_helper
+                      if ! ldd dist/apps/electron-backend/native/iptvnator_mpv_helper | grep -q 'libmpv'; then
+                          echo "::error::Linux frame-copy helper must link libmpv"
+                          ldd dist/apps/electron-backend/native/iptvnator_mpv_helper
+                          exit 1
+                      fi
                       ;;
                   esac
 

apps/electron-backend/native/helper/frame_helper_gl.h

@@ -212,18 +212,29 @@ public:
 
 private:
     bool acquireDisplay() {
+        /* Tier log goes to stderr (the adapter mirrors it) — stdout is
+         * reserved for the JSON event protocol. */
         display_ = eglGetPlatformDisplay(EGL_PLATFORM_SURFACELESS_MESA,
                                          nullptr, nullptr);
-        if (initDisplay(display_)) return true;
+        if (initDisplay(display_)) {
+            std::fprintf(stderr, "egl display: surfaceless-mesa\n");
+            return true;
+        }
 
         display_ = eglGetDisplay(EGL_DEFAULT_DISPLAY);
-        if (initDisplay(display_)) return true;
+        if (initDisplay(display_)) {
+            std::fprintf(stderr, "egl display: default\n");
+            return true;
+        }
 
         display_ = EGL_NO_DISPLAY;
         if (openGbmDevice()) {
             display_ = eglGetPlatformDisplay(EGL_PLATFORM_GBM_KHR, gbmDevice_,
                                              nullptr);
-            if (initDisplay(display_)) return true;
+            if (initDisplay(display_)) {
+                std::fprintf(stderr, "egl display: gbm render node\n");
+                return true;
+            }
         }
         display_ = EGL_NO_DISPLAY;
         return false;