Invite device reports via pre-filled GitHub issues

[mannes]

Brushlog is only confirmed on the Oral-B iO. This asks everyone else to tell us how their brush behaves, without getting in the way.

What the user sees

A dismissible, non-blocking toast (bottom right):

• A brush that isn't an iO connects → "Brushlog is only confirmed on the Oral-B iO so far. Does your brush work? Tell us how it went". Asked once per model: dismissing or reporting is remembered in localStorage. It waits for GATT discovery so the report includes the service layout. An iO gets no toast.
• The chooser is dismissed, or connecting fails → "Brush not in the list, or won't connect? Tell us which one". Dismissing hides it until the next cancel or failure.

Both open a pre-filled GitHub issue form in a new tab. The app sends nothing itself; the user reviews and submits on GitHub.

What's in the report

Connected: advertised name, model id / protocol / firmware, service and characteristic UUIDs with their properties, and the browser. No brushing data, no characteristic values, no raw frames. If we need a capture, we ask for the Diagnostics report in the thread.

Connection problem: the browser and the error message, if there was one.

Changes

• .github/ISSUE_TEMPLATE/device-report.yml and connection-problem.yml (labels device report / connection problem, both created)
• src/lib/report.ts builds the issue URLs; src/components/ReportToast.tsx shows the toast
• useBrush exposes cancelled (the last connect ended with the chooser dismissed)
• README: a paragraph under Compatibility

Testing

• npm run typecheck and npm run build pass
• Toast checked in desktop Chrome on the dev server, connected to a non-Oral-B device (unconfirmed case)
• Needs a hardware check: an iO connection shows no toast; dismissing the chooser shows the connection-problem toast

The forms only resolve on main, so the pre-filled links fall back to the plain issue picker until this merges.