supabase / supabase / 29083557100 / 1 – studio-tests

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fix(telemetry): dedupe funnel toast error events (#47802)

## Summary
Since #47293, an API failure on a signup / org-creation /
project-creation form emitted `dashboard_error_created` twice:
`useTrackFunnelError` fired the origin-tagged event and the global
`ToastErrorTracker` independently fired the legacy untagged
`source:'toast'` event for the same toast, each behind its own 10%
sampling draw. I verified the twin rate empirically at 8-11% of
origin-tagged funnel toasts, exactly the floor for two independent 10%
draws, meaning the twin co-fires for effectively every funnel error
([Hex
thread](https://app.hex.tech/supabase/thread/019f3bc1-3a5c-7200-9122-8e3439bfbe8c)).
Any consumer counting funnel errors without an `origin IS NOT NULL`
filter saw ~2x inflation.

The fix makes `ToastErrorTracker` the sole emitter of `source:'toast'`
events, so the duplicate is unrepresentable rather than suppressed.
Funnel call sites pass the id returned by `toast.error()` into
`trackFunnelError`, which registers the funnel properties against that
toast id instead of firing its own event – the tracker then emits a
single `dashboard_error_created` enriched with `origin` /
`errorCategory` / `errorReason` / `errorCode` for registered toasts, and
the plain untagged event otherwise. The `'toast'` overload of
`trackFunnelError` requires the toast id, so a missed pairing is a
compile error rather than a silent double count. Registration is
unconditional and there's only one sampling draw, so suppression can't
lose a sampling race. `'form'`-sourced funnel events are unchanged.

## Changes
- `lib/toast-errors.tsx`: toast-id → funnel-properties registry
(`registerFunnelErrorToast`); `ToastErrorTracker` emits one (optionally
enriched) event per error toast under a single 10% draw, deleting
entries once consumed
- `lib/telemetry/use-track-funnel-error.ts`: overloaded signature –
`'toast'` requires the id returned by `toast.error()` (type-enforced),
`'form'` keeps direct emission ... (continued)

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