fix(telemetry): attribute studio renders to the browser user (joinable funnel) (#1492)

Studio-triggered renders emit render_complete / render_error from the CLI
preview-server process, which stamps every event with the install's
anonymousId (client.ts drainQueueToPayload). The browser, meanwhile, fires
studio_session_start / studio_render_start under its own getAnonymousId(). So
the render outcome and the render start never share a person_id — verified in
data: of 15,125 users who started a studio render in 30d, ZERO have any
render_complete under any source, and the 898 studio-tagged completers are
disjoint server UUIDs. The studio render funnel — the product's core value
moment and strongest retention signal — is therefore unmeasurable.

Thread the browser's telemetry id through to the render-outcome events:

- client.ts: trackEvent takes an optional distinctId; drainQueueToPayload uses
  `event.distinctId ?? config.anonymousId`. CLI renders unchanged.
- events.ts: trackRenderComplete/trackRenderError forward an optional distinctId.
- studioRenderTelemetry.ts: emitStudioRender* pass opts.distinctId through.
- core studio-api (types.ts + routes/render.ts): the render route reads
  `telemetryDistinctId` from the request body (validated string) and passes it
  to the adapter's startRender, which already forwards opts to the emitters.
- studio (useRenderQueue.ts): include getAnonymousId() as telemetryDistinctId
  in the render POST — the same id studio_* events already use.

Result: studio render_complete/error now carry the browser user's id and join
studio_session_start / studio_render_start. Older clients that don't send the
field fall back to anonymousId (no regression). No new tracking surface — it's
the existing anonymous studio id.

Tests: per-event override forwarding (events), studio render distinctId
threading + older-client fallback (studioRenderTelemetry), and route body →
adapter forwarding incl. non-string rejection (core render route).

packages/studio/src/components/renders/useRenderQueue.ts

@@ -1,5 +1,6 @@
 import { useState, useEffect, useCallback, useRef, useMemo } from "react";
 import { trackStudioRenderStart } from "../../telemetry/events";
+import { getAnonymousId } from "../../telemetry/config";
 
 export interface RenderJob {
   id: string;
@@ -109,10 +110,15 @@ export function useRenderQueue(projectId: string | null) {
         format: string;
         resolution?: string;
         composition?: string;
+        telemetryDistinctId: string;
       } = {
         fps,
         quality,
         format,
+        // So the server-emitted render_complete/render_error is attributed to
+        // this browser user (same id studio_* events use), making the render
+        // funnel joinable. Matches studio_render_start fired just above.
+        telemetryDistinctId: getAnonymousId(),
       };
       if (resolution && resolution !== "auto") body.resolution = resolution;
       if (composition) body.composition = composition;