WIP fix(cloudflare): Keep http root span alive until streaming responses are consumed

[RulaKhaled]

Fixes: https://linear.app/getsentry/issue/JS-1103/spans-are-not-flushed-to-dashboard-when-using-streamtext-with-vercel

The Cloudflare request wrapper was ending the root HTTP span immediately when the handler returned a streaming Response (e.g. result.toTextStreamResponse()). Since Vercel AI child spans only finish after the stream is consumed by the client, they were filtered out by Sentry's isFullFinishedSpan check, resulting in transactions with 0 spans.

---

This PR implements a streaming response detection and handles this from within the http handler:

1. Created classifyResponseStreaming() helper

   • Detects streaming via Content-Type (SSE), Content-Length, or stream probing
   • Returns original Response when possible, teed Response when probed

2. Updated request wrapper

   • Changed from startSpan() to startSpanManual() for manual span control
   • Monitors streaming response consumption in background
   • Ends root span only after stream fully consumed by client

[linear]

JS-1103 Spans are not flushed to dashboard when using streamText() with Vercel AI SDK in Cloudflare Workers

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	24.64 kB	-	-
@sentry/browser - with treeshaking flags	23.13 kB	-	-
@sentry/browser (incl. Tracing)	41.26 kB	-	-
@sentry/browser (incl. Tracing, Profiling)	45.54 kB	-	-
@sentry/browser (incl. Tracing, Replay)	79.51 kB	-	-
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	69.2 kB	-	-
@sentry/browser (incl. Tracing, Replay with Canvas)	84.21 kB	-	-
@sentry/browser (incl. Tracing, Replay, Feedback)	96.38 kB	-	-
@sentry/browser (incl. Feedback)	41.31 kB	-	-
@sentry/browser (incl. sendFeedback)	29.31 kB	-	-
@sentry/browser (incl. FeedbackAsync)	34.24 kB	-	-
@sentry/react	26.32 kB	-	-
@sentry/react (incl. Tracing)	43.24 kB	-	-
@sentry/vue	29.13 kB	-	-
@sentry/vue (incl. Tracing)	43.05 kB	-	-
@sentry/svelte	24.65 kB	-	-
CDN Bundle	26.9 kB	-	-
CDN Bundle (incl. Tracing)	41.8 kB	-	-
CDN Bundle (incl. Tracing, Replay)	78.07 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback)	83.56 kB	-	-
CDN Bundle - uncompressed	78.89 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	124.01 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	239.2 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	251.96 kB	-	-
@sentry/nextjs (client)	45.36 kB	-	-
@sentry/sveltekit (client)	41.67 kB	-	-
@sentry/node-core	50.81 kB	-	-
@sentry/node	157.88 kB	-	-
@sentry/node - without tracing	92.69 kB	-	-
@sentry/aws-serverless	106.42 kB	-	-

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