Fix GL viewport sizing and ship a real playable default table

The OpenGL back-buffer render target was created with the window's
logical/CSS size instead of its device-pixel size, so on any browser
tab with devicePixelRatio != 1 the GL viewport only covered a fraction
of the canvas's actual backing buffer (rendering anchored bottom-left,
matching GL's viewport origin) - confirmed against a live repro and
fixed to match the convention already used by the BGFX backend
elsewhere in the same file.

Also swap the bundled default table from test000-default-table.vpx
(upstream's rendering/component regression-test fixture, which has no
gameplay script) to exampleTable.vpx - a genuine playable demo table
with working flippers, slingshots, bumpers, targets and a plunger -
confirmed keyboard input and audio now work end-to-end through it.

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

scripts/build.sh

@@ -45,7 +45,7 @@ EMSCRIPTEN_LINK_FLAGS=(
    -sENVIRONMENT=web
    -sEXPORTED_RUNTIME_METHODS=FS,ccall,cwrap
    -sFORCE_FILESYSTEM=1
-   -sEXPORTED_FUNCTIONS=_main,_vpinball_wasm_start,_vpinball_wasm_stop,_vpinball_wasm_dispose
+   -sEXPORTED_FUNCTIONS=_main,_vpinball_wasm_start,_vpinball_wasm_stop,_vpinball_wasm_dispose,_vpinball_wasm_eval_script
    -sEXIT_RUNTIME=0
    --use-preload-cache
 )
@@ -80,7 +80,7 @@ cp "$BUILD_DIR"/vpinball.wasm "$DIST_DIR/" 2>/dev/null || true
 cp "$BUILD_DIR"/vpinball.data "$DIST_DIR/" 2>/dev/null || true
 
 mkdir -p "$ROOT_DIR/package/assets"
-cp "$VPINBALL_DIR/tests/assets/test000-default-table.vpx" "$ROOT_DIR/package/assets/default.vpx" 2>/dev/null || true
+cp "$VPINBALL_DIR/src/assets/exampleTable.vpx" "$ROOT_DIR/package/assets/default.vpx" 2>/dev/null || true
 
 echo ""
 echo "== build.sh complete =="