tracing: Log to stderr, and drop timestamps

[cgwalters]

This matches bootc's setup (without the journal integration for now as we don't strictly need it).

But specifically this fixes setting RUST_LOG and having that break the monitor-status JSON stream:
#86 (comment)

[gemini-code-assist]

Code Review

This pull request refactors the tracing setup to prevent log messages from interfering with JSON output on standard output. The changes correctly configure logging to use standard error, remove timestamps, and apply a compact format. The implementation in crates/kit/src/main.rs is sound and effectively uses the tracing-subscriber API. I have one suggestion to improve code conciseness.

[gemini-code-assist]

Since the format variable is only used once, you could consider inlining its definition directly into the .event_format() call. This would make the fmt_layer configuration more concise and express it as a single fluent chain of calls, which is a common pattern when using builders in Rust.

Suggested change

	let format = fmt::format().without_time().with_target(false).compact();
	let fmt_layer = fmt::layer()
	.event_format(format)
	.with_writer(std::io::stderr);
	let fmt_layer = fmt::layer()
	.event_format(fmt::format().without_time().with_target(false).compact())
	.with_writer(std::io::stderr);