[Feature]: Capture script invocation telemetry

Currently we capture plugin telemetry on skill invocations and reference file reads. Skills now include an increasing number of scripts. We should report a telemetry event every time a skill script is invoked--basically, what we do for reference file reads, but for scripts.

Start by locating the existing telemetry implementation for skill invocations and reference file reads, then trace how those events are emitted. Add equivalent coverage for every skill script invocation and verify that the telemetry event is reported consistently with reference file reads.

Written by the indexing model from the issue text.