feat: pl_editor WASM port + browser file dialog fixes

Brings up KiCad's pagelayout_editor (drawing-sheet editor) in the
browser, to roughly the same "boots, canvas visible, partially usable
in-session" level as the existing pcbnew/eeschema/calculator ports.

Build:
- docker/build.sh: add pl_editor to the unified app dispatch (case,
  subdir map, all-loop).
- scripts/kicad/build-kicad-target.sh: add pl_editor to the case;
  upstream target name pl_editor under source subdir pagelayout_editor.
- scripts/kicad/build-pl_editor.sh: 7-line thin wrapper matching the
  pcbnew/eeschema/calculator pattern.
- tests/scripts/setup-kicad-wasm.sh: copy_app pl_editor.

App glue:
- wasm/stubs/nl_pl_editor_plugin_stub.cpp: no-op SpaceMouse plugin so
  pl_editor_frame.cpp's NL_PL_EDITOR_PLUGIN symbols resolve. Mirrors
  nl_pcbnew_plugin_stub.cpp.
- tests/apps/kicad/pl_editor.html: browser shell. preRun creates
  /home/kicad and FS.chdir there so file dialogs land somewhere
  friendly instead of MEMFS root (/dev/, /proc/, etc.).

E2E coverage:
- tests/kicad/pl_editor.spec.ts: 5 tests — smoke (canvas, no abort),
  wizard, File menu has Open/Save As, file-dialog folder-navigation
  regression, canvas + toolbar metrics.
- tests/e2e/filedialog-folder-nav.spec.ts: wxWidgets-level twin of
  the regression test (exercises the underlying widget directly via
  the standalone filedialog_test app).

Submodule bumps:
- kicad → feature/pl-editor (WASM gating in pagelayout_editor's
  CMakeLists + navlib stub).
- wxwidgets → feature/pl-editor (wxGenericFileDialog::OnOk navigates
  into selected directories; wasm/mouse.cpp emits wxEVT_LEFT_DCLICK
  via timestamp-based double-click detection — the latter benefits
  every wxWidgets-WASM app).

See features/pl-editor/ for the design doc + per-repo diff patches.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/kicad/build-kicad-target.sh

@@ -1,11 +1,11 @@
 #!/bin/bash
-# Build a KiCad app (pcbnew, eeschema, calculator) for WebAssembly.
+# Build a KiCad app (pcbnew, eeschema, calculator, pl_editor) for WebAssembly.
 #
 # Usage:
 #   ./scripts/kicad/build-kicad-target.sh <app> [options]
 #
 # Args:
-#   <app>         pcbnew | eeschema | calculator (required)
+#   <app>         pcbnew | eeschema | calculator | pl_editor (required)
 #
 # Options:
 #   --full        Full clean rebuild (dependencies + KiCad)
@@ -26,25 +26,26 @@
 # the source subdirectory. Calculator is the exception: app=calculator but the
 # upstream target and source subdir are both pcb_calculator (the OUTPUT_NAME
 # property in pcb_calculator/CMakeLists.txt emits calculator.{js,wasm}).
+# pl_editor is the standard case but its source subdir is pagelayout_editor.
 
 set -e
 
 if [ -z "$1" ]; then
-    echo "Error: missing <app> argument (pcbnew | eeschema | calculator)" >&2
+    echo "Error: missing <app> argument (pcbnew | eeschema | calculator | pl_editor)" >&2
     exit 1
 fi
 APP_NAME="$1"
 shift
 
 case "$APP_NAME" in
-    pcbnew|eeschema)
+    pcbnew|eeschema|pl_editor)
         KICAD_TARGET="$APP_NAME"
         ;;
     calculator)
         KICAD_TARGET="pcb_calculator"
         ;;
     *)
-        echo "Error: unknown app '$APP_NAME' (expected: pcbnew | eeschema | calculator)" >&2
+        echo "Error: unknown app '$APP_NAME' (expected: pcbnew | eeschema | calculator | pl_editor)" >&2
         exit 1
         ;;
 esac

scripts/kicad/build-pl_editor.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+# Build KiCad pl_editor (drawing-sheet editor) for WebAssembly.
+# Thin wrapper around build-kicad-target.sh — see that script for options.
+
+set -e
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+exec "${SCRIPT_DIR}/build-kicad-target.sh" pl_editor "$@"