telemetry: document tool-call and MCP client rows

[arrufat]

Updates the list of what local telemetry collects to cover lightpanda-io/browser#3820:

• tool calls: counts per tool, caller (agent, agent script or MCP client) and outcome, with total duration
• which known MCP client is connected, from a fixed list (the raw client name is never sent)

Also states that tool arguments are never sent.

Draft until lightpanda-io/browser#3820 merges.

[cdebled]

Related subject: do we have telemetry on the python package? If so, could people disable it?

[arrufat]

Well, there's no telemetry stuff in the python package, but since the python package launches the lightpanda binary in the background, it will respect the environment variable LIGHTPANDA_DISABLE_TELEMETRY.