move Rhai output indicator to log level

[wyatt-avilla]

Currently, we route Rhai script outputs like this:

cli/src/response_provider/custom/provider.rs

Lines 27 to 30 in 6d4d68c

	engine.on_print(|s| tracing::info!("[rhai] {s}"));
	engine.on_debug(|s, src, pos| {
	tracing::debug!("[rhai] {s} @ {src:?}:{pos}");
	});

Prints end up rendering like this:

2026-02-27T20:09:44.512946Z  INFO cbl::response_provider::custom::provider: [rhai] message goes here

Rhai info messages are distinguished from Rust info messages via the [rhai] prefix. This should be moved into the log level instead for clarity (e.g., RHAI_INFO instead of INFO)