Add browser reader with local library and offline support

[Zer0codestuff]

Rapid Reader currently runs on macOS. This adds a separate browser app in web/, with the native amber identity, focus-letter RSVP stage, text mode and floating glass controls.

The web app supports all existing file formats, chapter navigation, search, favorites, editable position-linked notes, progress, per-document pacing, reading defaults, themes and statistics. IndexedDB keeps documents and metadata local. It also has a responsive library drawer, offline reading and JSON backup/restore. The Express server only serves the app and retrieves public article text; it never stores local documents. The native source and library are unchanged.

Validation:

• 23 core, import, persistence and article-service tests pass.
• TypeScript, release build, clean npm install and dependency audit pass. Zero vulnerabilities.
• Complete isolated Chromium and WebKit browser QA passes: imports, playback, text selection, search, notes, stats, backups, deletion, mobile layouts, themes and cached reload.
• WebKit uses a stopped local server for offline QA because Playwright's offline emulation blocks its service worker before navigation.
• Physical mobile devices, native Safari, Firefox and assistive technologies were not tested.

Published through the Railway plugin at rapid-reader.up.railway.app, in the new Rapid Reader project and live environment. Chromium and WebKit checks also pass on the public HTTPS site; Chromium verified offline reload there. Public Wikipedia article import succeeds.

The Railway service builds /web from this branch. Root and web AGENTS.md files, web README and docs/validation.md describe the architecture, privacy constraints, deployment and verification.