fix(core): Ensure tool calls are recorded in invoke_agent spans

[nicohrubec]

Still investigating this.

[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	9,003	-	8,690	+4%
GET With Sentry	1,376	15%	1,397	-2%
GET With Sentry (error only)	6,099	68%	6,120	-0%
POST Baseline	1,198	-	1,213	-1%
POST With Sentry	511	43%	561	-9%
POST With Sentry (error only)	1,054	88%	1,072	-2%
MYSQL Baseline	3,321	-	3,363	-1%
MYSQL With Sentry	476	14%	482	-1%
MYSQL With Sentry (error only)	2,724	82%	2,713	+0%

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