feat(core): Migrate Vercel AI event processor to span streaming

[nicohrubec]

Migrates the Vercel AI event processor so it also works in the span streaming path via the processSpan hook. The event processor currently serves three purposes:

Attribute renaming. The Vercel AI SDK emits attributes under ai.* names that need to be renamed to OpenTelemetry semantic conventions (gen_ai.*) and the vercel.ai.* namespace. This logic is straightforward to port. It's extracted into a shared processVercelAiSpanAttributes helper that is now called from both the legacy event processor path (for transactions) and the new processSpan hook (for streamed spans).

Token accumulation on parent spans. The event processor aggregates token usage from child spans onto their parent invoke_agent spans. This is a cross-span operation that fundamentally doesn't work in the streaming model where spans are processed individually. The span streaming implementation guide explicitly lists this as a case that cannot be replaced. Since the plan is for parent-level token accumulation to go away regardless, we simply drop it for the streaming path.

Tool descriptions on execute_tool spans. The event processor iterates over all spans in a transaction to find gen_ai.request.available_tools on doGenerate spans and applies the matching description to sibling execute_tool spans. This cross-span iteration doesn't work when spans are processed individually. Instead, we parse and store tool descriptions in a map at spanStart time of the doGenerate span. Since execute_tool spans are siblings of doGenerate (both children of invoke_agent), we key the map by the parent span ID so execute_tool spans can look up descriptions by their own parent_span_id. This assumes a flat sibling hierarchy, which holds for our test scenarios. If we encounter more complex cases down the road, I think it's fine to address in a follow-up.

Closes#20377

[github-actions]

size-limit report 📦

Path	Size	% Change	Change
@sentry/browser	26.3 kB	-	-
@sentry/browser - with treeshaking flags	24.78 kB	-	-
@sentry/browser (incl. Tracing)	44.17 kB	-	-
@sentry/browser (incl. Tracing + Span Streaming)	46.39 kB	-	-
@sentry/browser (incl. Tracing, Profiling)	49.14 kB	-	-
@sentry/browser (incl. Tracing, Replay)	83.55 kB	-	-
@sentry/browser (incl. Tracing, Replay) - with treeshaking flags	73.01 kB	-	-
@sentry/browser (incl. Tracing, Replay with Canvas)	88.23 kB	-	-
@sentry/browser (incl. Tracing, Replay, Feedback)	100.84 kB	-	-
@sentry/browser (incl. Feedback)	43.44 kB	-	-
@sentry/browser (incl. sendFeedback)	31.11 kB	-	-
@sentry/browser (incl. FeedbackAsync)	36.19 kB	-	-
@sentry/browser (incl. Metrics)	27.6 kB	-	-
@sentry/browser (incl. Logs)	27.73 kB	-	-
@sentry/browser (incl. Metrics & Logs)	28.43 kB	-	-
@sentry/react	28.04 kB	-	-
@sentry/react (incl. Tracing)	46.4 kB	-	-
@sentry/vue	31.18 kB	-	-
@sentry/vue (incl. Tracing)	46.02 kB	-	-
@sentry/svelte	26.32 kB	-	-
CDN Bundle	28.91 kB	-	-
CDN Bundle (incl. Tracing)	46.94 kB	-	-
CDN Bundle (incl. Logs, Metrics)	30.34 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics)	48.04 kB	-	-
CDN Bundle (incl. Replay, Logs, Metrics)	69.4 kB	-	-
CDN Bundle (incl. Tracing, Replay)	84.07 kB	-	-
CDN Bundle (incl. Tracing, Replay, Logs, Metrics)	85.15 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback)	89.89 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics)	90.97 kB	-	-
CDN Bundle - uncompressed	84.88 kB	-	-
CDN Bundle (incl. Tracing) - uncompressed	140.44 kB	-	-
CDN Bundle (incl. Logs, Metrics) - uncompressed	89.08 kB	-	-
CDN Bundle (incl. Tracing, Logs, Metrics) - uncompressed	143.9 kB	-	-
CDN Bundle (incl. Replay, Logs, Metrics) - uncompressed	212.99 kB	-	-
CDN Bundle (incl. Tracing, Replay) - uncompressed	258.24 kB	-	-
CDN Bundle (incl. Tracing, Replay, Logs, Metrics) - uncompressed	261.69 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback) - uncompressed	271.94 kB	-	-
CDN Bundle (incl. Tracing, Replay, Feedback, Logs, Metrics) - uncompressed	275.38 kB	-	-
@sentry/nextjs (client)	48.9 kB	-	-
@sentry/sveltekit (client)	44.64 kB	-	-
@sentry/node-core	59.81 kB	+0.02%	+10 B 🔺
@sentry/node	163.56 kB	+0.09%	+144 B 🔺
@sentry/node - without tracing	72.28 kB	+0.02%	+9 B 🔺
@sentry/aws-serverless	106.95 kB	+0.01%	+7 B 🔺
@sentry/cloudflare (withSentry) - minified	168.38 kB	-	-
@sentry/cloudflare (withSentry)	424.9 kB	-	-

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[chargome]

Thanks for updating! LGTM now, I just hope we didn't overlook any edge cases where the map might leak 📿