Repair current-main native Runtime CI bootstrap and Dawn fixtures

[wieslawsoltes]

Problem

Current WebScene main at 7955519 cannot produce the native Runtime packages required by the AppScene and unchanged Code OSS release.

• Native package run 35505459479 fails on both Windows and Linux while extracting V8 snapshot bootstraps: the final raw literal in install_editor_web_platform_globals is 16,539 UTF-8 bytes, exceeding the intentional 15,000-byte ceiling that keeps MSVC below C2026's 16,380-byte literal limit.
• General CI run 35505459474 fails eng.graphics.tests.test_dawn_exports on Linux. The Windows fixture supplies only wgpuCreateInstance and wgpuGetProcAddress, but production correctly requires the merged exact-device bridge export websceneDawnQueryD3D12DeviceV1.

The macOS legs were cancelled after required jobs failed so the shared runner could service the current AppScene CLI build.

Proposed fix

1. Split the oversized final editor-platform raw JavaScript literal at a statement boundary. Preserve ordered byte-for-byte concatenation through the existing source_parts array and snapshot extractor; do not raise the safety ceiling.
2. Update the Windows export-format fixture to contain websceneDawnQueryD3D12DeviceV1, retaining the exact required export set.
3. Add a focused regression contract that every extracted raw literal stays within the portable ceiling and that extraction joins all parts in source order.

Acceptance

• The bootstrap extractor succeeds and reports every part at or below 15,000 bytes.
• Extracted snapshot JavaScript equals the runtime source_parts concatenation.
• Windows, Linux, and macOS native Runtime package jobs configure successfully.
• General graphics boundary tests pass with the exact Windows bridge export.
• No JavaScript behavior, generated snapshot bytes, or public ABI changes beyond the already merged D3D12 bridge.

Coordination

Blocks AppScene SDK producer run 35507539063, AppScene #307, WebScene #809, and the VS Code OSS consolidation release.