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",
 ]

crates/maestro/Cargo.toml

@@ -29,3 +29,6 @@ tracing-subscriber.workspace = true
 maestro-cli = { path = "../maestro-cli", optional = true, default-features = false }
 maestro-daemon = { path = "../maestro-daemon", optional = true, default-features = false }
 maestro-tui = { path = "../maestro-tui", optional = true }
+
+[dev-dependencies]
+tempfile.workspace = true

crates/maestro/tests/subcommand_routing.rs

@@ -0,0 +1,102 @@
+//! Process-level routing for the umbrella `maestro` binary (#10): each
+//! enabled top-level subcommand must reach its own crate's runtime dispatch,
+//! not just parse successfully.
+//!
+//! A malformed `--config` file makes every crate's dispatch fail identically
+//! at config load, before any subcommand touches tmux, the network, or a
+//! terminal. That lets the assertions tell "clap parsed it but the handler
+//! never ran" (a usage error, exit 2) apart from "it dispatched into the real
+//! crate" (a `toml decode` runtime error via `main`'s `maestro: {e}` printer,
+//! exit 1).
+//!
+//! The absence tests below only compile when the matching feature is off, so
+//! they run under CI's per-feature-subset matrix (`--no-default-features
+//! --features cli|daemon|tui`) rather than the default all-features build.
+
+use std::io::Write;
+use std::path::PathBuf;
+use std::process::{Command, Output};
+
+fn bin() -> PathBuf {
+    PathBuf::from(env!("CARGO_BIN_EXE_maestro"))
+}
+
+fn bad_config() -> tempfile::NamedTempFile {
+    let mut f = tempfile::NamedTempFile::new().expect("create temp config file");
+    write!(f, "this is not valid toml {{{{{{").expect("write temp config");
+    f
+}
+
+fn run(args: &[&str]) -> Output {
+    Command::new(bin())
+        .args(args)
+        .output()
+        .unwrap_or_else(|e| panic!("spawn `maestro {args:?}`: {e}"))
+}
+
+/// Real dispatch happened: exit 1, `main`'s `"maestro: {e}"` prefix, and the
+/// config crate's error surfacing through — never clap's own usage-error
+/// page, which would mean the subcommand never reached its handler.
+fn assert_dispatched(out: &Output) {
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert_eq!(out.status.code(), Some(1), "stderr:\n{stderr}");
+    assert!(stderr.starts_with("maestro: "), "stderr:\n{stderr}");
+    assert!(stderr.contains("toml decode"), "stderr:\n{stderr}");
+    assert!(!stderr.contains("Usage:"), "stderr:\n{stderr}");
+}
+
+/// Never reached a handler: clap rejected the subcommand outright because the
+/// feature that defines it is off. Only used by the `not(feature = "...")`
+/// tests below, which themselves only exist in a single-feature build.
+#[cfg(not(all(feature = "cli", feature = "daemon", feature = "tui")))]
+fn assert_unrecognized(out: &Output, name: &str) {
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert_eq!(out.status.code(), Some(2), "stderr:\n{stderr}");
+    assert!(
+        stderr.contains("unrecognized subcommand"),
+        "stderr:\n{stderr}"
+    );
+    assert!(stderr.contains(name), "stderr:\n{stderr}");
+}
+
+#[cfg(feature = "cli")]
+#[test]
+fn list_dispatches_into_maestro_cli() {
+    let cfg = bad_config();
+    let out = run(&["list", "--config", cfg.path().to_str().unwrap()]);
+    assert_dispatched(&out);
+}
+
+#[cfg(not(feature = "cli"))]
+#[test]
+fn list_is_unrecognized_without_cli_feature() {
+    assert_unrecognized(&run(&["list"]), "list");
+}
+
+#[cfg(feature = "daemon")]
+#[test]
+fn daemon_dispatches_into_maestro_daemon() {
+    let cfg = bad_config();
+    let out = run(&["daemon", "--config", cfg.path().to_str().unwrap()]);
+    assert_dispatched(&out);
+}
+
+#[cfg(not(feature = "daemon"))]
+#[test]
+fn daemon_is_unrecognized_without_daemon_feature() {
+    assert_unrecognized(&run(&["daemon"]), "daemon");
+}
+
+#[cfg(feature = "tui")]
+#[test]
+fn tui_dispatches_into_maestro_tui() {
+    let cfg = bad_config();
+    let out = run(&["tui", "--config", cfg.path().to_str().unwrap()]);
+    assert_dispatched(&out);
+}
+
+#[cfg(not(feature = "tui"))]
+#[test]
+fn tui_is_unrecognized_without_tui_feature() {
+    assert_unrecognized(&run(&["tui"]), "tui");
+}