v0.1.1

feat: browser extension integration (native host + drift companion)

- Add drift-host native messaging relay, registered at runtime with Chrome/Firefox (host manifest + registry keys); live status in Settings -> Browser integration

- Thread referrer through probe and download requests so hotlink-protected handoffs work

- Extend drift://add deep links with filename and referrer hints

- Add drift companion extension (MV3): auto-captures browser downloads when drift is installed, right-click menus, subtle install nudge when it isn't

- Dedupe deep-link delivery and re-triggered downloads (one save dialog per handoff); silent handoff when auto-save is enabled

- Rebrand extension icons from public/drift.png; bundle drift-host via externalBin (scripts/build-host.mjs + CI step)

- Bump version to 0.1.1