Problem

Today, src/webview-preload.js listens for file-drop and logs file paths but does not actually trigger NotebookLM's upload pipeline. Constructing a synthetic file-drop DataTransfer event across the webview security boundary is not straightforward — File objects with real bytes are needed by NotebookLM's dropzone.

NotebookLM's native dropzone DOES accept drops, but only when the user drops directly onto NotebookLM's dropzone region — not when they drop anywhere on the window.

Proposed approach

A few options worth exploring:

1. Read file → construct File via fetch: From the webview, fetch a file:// URL of the dropped path, build a File from the response Blob, dispatch a synthetic drop on NotebookLM's dropzone. Investigate whether webview security allows file:// reads.
2. Auto-click NotebookLM's "+ Add source" + invoke <input type=file>: Locate the file input via DOM selectors and set its .files via DataTransfer. Selector stability is the risk.
3. Forward to system clipboard + paste: Last-resort fallback for image files.

Files to touch

• src/webview-preload.js — file-drop handler
• src/renderer.js — pass file paths (already done)
• src/main.js — may need a file-read helper exposed via IPC

Acceptance criteria

• Dropping a PDF anywhere on the window produces the same outcome as dropping it on NotebookLM's dropzone.
• Gracefully falls back to a "drop on the central area" toast if the upload fails.
• Works for PDF, TXT, Markdown at minimum.