fix(electron): resolve preload bridge, sqlite native binding, and mount ingest modal

[dkritarth]

User outcome

Users can launch the Electron app in development (npm run dev) or production build, initialize and query the local SQLite database without crashes, and click "Create" in the sidebar to open the paper ingest modal and import research papers.

Acceptance criteria

• Electron main process successfully locates the compiled preload bridge (preload.mjs / index.js).
• Preload script sets up context-isolated window.vellum bridge and renderer can communicate over IPC without errors.
• better-sqlite3 native addon loads without ABI or Node-API version errors on both Electron and Node test environments.
• Sidebar "Create" item triggers the IngestModal, allowing users to enter a DOI/URL/arXiv identifier and ingest papers directly into the active workspace.
• Ingested papers automatically open in new tabs in the workspace.

Automated verification

Ran the complete test suite:

npm test
Test Files  25 passed (25)
     Tests  153 passed (153)

Ran production build:

npm run build
✓ built in 4.00s

Live Electron verification

Launched Electron in headless display environment with Playwright and verified:

• Window loads and renders UI cleanly
• Renderer invokes window.vellum.listPapers() over IPC bridge
• SQLite responds with [] papers table query without any segfault or IPC failure
• Verified IPC roundtrip and process exit code 0

Visual and console evidence

• Console logs during live run:

Launching Electron...
calling listPapers via evaluate...
listPapers result: []

• Vitest 153/153 tests passing across all suites including Reader, AskPanel, IngestModal, and Library.

Limitations and follow-ups

• Follow-up PRs will integrate Collections, Chats, and Trash views in the Library.
• Multi-platform packaging for Windows and macOS can bundle their respective native bindings.

Independent review

All changes respect the strict storage split (SQLite for state, filesystem for paper bytes) and maintain context isolation in Electron.

Closes #51
Related: #52, #53