test(maestro): verify umbrella binary routes each subcommand to its crate

Closes #10

The compile_error guard and per-feature build already had CI coverage
(the "feature-gate matrix" job). What was missing was proof that a
subcommand actually reaches its own crate's dispatch at runtime, not
just that clap parses it.

A malformed --config file makes cli/daemon/tui fail identically at
config load, before touching tmux, the network, or a terminal. That
turns "clap parsed it but the handler never ran" (a usage error, exit
2) into a distinguishable outcome from "it dispatched into the real
crate" (a `toml decode` runtime error via main's error printer, exit
1). The absence-side tests are feature-gated to only exist in a
single-feature build, so they run under CI's existing per-feature
matrix rather than the default all-features build.

Cargo.lock

@@ -1051,6 +1051,7 @@ dependencies = [
  "maestro-cli",
  "maestro-daemon",
  "maestro-tui",
+ "tempfile",
  "tokio",
  "tracing-subscriber",
 ]