Error code lines diagnostics with multi-level, nested includes support

[ChemistAion]

• Fixes incorrect error line/file attribution when shaders use nested #include.
• Uses GLSL #line with per-include source IDs so WebGL compiler logs [ERROR : sourceId : line] map back to the correct file and line.
• Include expansion emits #line 1 <id> for the included file, then resumes the parent with a self-source sentinel (65535) that is re-written at each nesting level.
• Webview maintains sourceID-to-file mapping and the error overlay displays clickable links and shows the source file path next to each error.

Example: demos/blobby.glsl