feat(maestro): scaffold maestro-tui crate + maestro tui subcommand (NAP-276)

New `crates/maestro-tui/` library behind a `tui` cargo feature on the umbrella
binary (default-on). Ships a clap-derive `TuiArgs` and a `run()` stub that
returns `NotImplemented` — exercises the full dispatch path so phases 2+ can
fill in the catalog, session liveness, widgets, and event loop without
touching scaffolding.

Acceptance:
- `cargo build -p maestro --features tui` succeeds
- `maestro tui` prints "maestro: not implemented" and exits 1
- `cargo test -p maestro-tui` passes (2 clap-parse tests)
- `cargo fmt --check` + `cargo clippy --all-targets --features tui -- -D warnings` clean

Phase 1 of the Maestro TUI epic (NAP-275); plan in
`docs/superpowers/plans/2026-05-28-maestro-tui.md`.

crates/maestro-tui/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "maestro-tui"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+publish.workspace = true
+description = "Terminal UI client over the local maestro daemon's `/api/*` surface."
+
+[dependencies]
+clap.workspace = true
+thiserror.workspace = true

crates/maestro-tui/src/cli.rs

@@ -0,0 +1,40 @@
+//! Clap-derive subcommand definition for `maestro tui`.
+
+#[derive(Debug, clap::Args)]
+pub struct TuiArgs {
+    /// Override the local daemon's HTTP base URL (default `http://127.0.0.1:7070`).
+    #[arg(long, env = "MAESTRO_DAEMON_URL")]
+    pub daemon_url: Option<String>,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use clap::Parser;
+
+    #[derive(Debug, Parser)]
+    struct Harness {
+        #[command(subcommand)]
+        cmd: Cmd,
+    }
+
+    #[derive(Debug, clap::Subcommand)]
+    enum Cmd {
+        Tui(TuiArgs),
+    }
+
+    #[test]
+    fn parses_with_daemon_url() {
+        let h = Harness::try_parse_from(["maestro", "tui", "--daemon-url", "http://10.0.0.1:7070"])
+            .unwrap();
+        let Cmd::Tui(args) = h.cmd;
+        assert_eq!(args.daemon_url.as_deref(), Some("http://10.0.0.1:7070"));
+    }
+
+    #[test]
+    fn parses_without_daemon_url() {
+        let h = Harness::try_parse_from(["maestro", "tui"]).unwrap();
+        let Cmd::Tui(args) = h.cmd;
+        assert!(args.daemon_url.is_none());
+    }
+}

crates/maestro-tui/src/lib.rs

@@ -0,0 +1,32 @@
+//! `maestro tui` — terminal UI client over the local daemon's `/api/*` surface.
+//!
+//! Design:         `docs/superpowers/specs/2026-05-28-maestro-tui-design.md`
+//! Implementation: `docs/superpowers/plans/2026-05-28-maestro-tui.md`
+//!
+//! Phase 1 (NAP-276) scaffolds the crate and a `Tui` subcommand stub. The real
+//! event loop, rendering, and `/api/*` plumbing land in NAP-277 onward.
+
+#![deny(missing_debug_implementations)]
+
+pub mod cli;
+
+/// Inputs for [`run`]. Built by the umbrella binary from the parsed
+/// `TuiArgs` plus any global flags.
+#[derive(Debug, Clone)]
+pub struct RunConfig {
+    /// HTTP base URL of the local daemon, e.g. `http://127.0.0.1:7070`.
+    /// No trailing slash.
+    pub daemon_url: String,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum TuiError {
+    #[error("not implemented")]
+    NotImplemented,
+}
+
+/// Entry point. Phase-1 stub — returns `NotImplemented` so the subcommand
+/// dispatch path is exercisable end-to-end before the renderer lands.
+pub async fn run(_cfg: RunConfig) -> Result<(), TuiError> {
+    Err(TuiError::NotImplemented)
+}

crates/maestro/Cargo.toml

@@ -12,10 +12,11 @@ name = "maestro"
 path = "src/main.rs"
 
 [features]
-default = ["cli", "daemon", "registry"]
+default = ["cli", "daemon", "registry", "tui"]
 cli = ["dep:maestro-cli"]
 daemon = ["dep:maestro-daemon"]
 registry = ["dep:maestro-registry"]
+tui = ["dep:maestro-tui"]
 
 [dependencies]
 clap.workspace = true
@@ -24,3 +25,4 @@ tracing-subscriber.workspace = true
 maestro-cli = { path = "../maestro-cli", optional = true }
 maestro-daemon = { path = "../maestro-daemon", optional = true }
 maestro-registry = { path = "../maestro-registry", optional = true }
+maestro-tui = { path = "../maestro-tui", optional = true }

crates/maestro/src/main.rs

@@ -7,8 +7,13 @@
 //! cargo install maestro                                              # default: cli + daemon + registry
 //! ```
 
-#[cfg(not(any(feature = "cli", feature = "daemon", feature = "registry")))]
-compile_error!("at least one of the `cli`, `daemon`, `registry` features must be enabled");
+#[cfg(not(any(
+    feature = "cli",
+    feature = "daemon",
+    feature = "registry",
+    feature = "tui"
+)))]
+compile_error!("at least one of the `cli`, `daemon`, `registry`, `tui` features must be enabled");
 
 use std::path::PathBuf;
 use std::process::ExitCode;
@@ -73,6 +78,10 @@ enum Command {
     /// Always-on registry: presence index + session catalog.
     #[cfg(feature = "registry")]
     Registry,
+
+    /// Open the terminal UI.
+    #[cfg(feature = "tui")]
+    Tui(maestro_tui::cli::TuiArgs),
 }
 
 fn main() -> ExitCode {
@@ -153,6 +162,13 @@ async fn dispatch(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
         Command::Daemon { cmd } => maestro_daemon::cli::dispatch(cli.config, cmd).await?,
         #[cfg(feature = "registry")]
         Command::Registry => maestro_registry::run(cli.config).await?,
+        #[cfg(feature = "tui")]
+        Command::Tui(args) => {
+            let daemon_url = args
+                .daemon_url
+                .unwrap_or_else(|| "http://127.0.0.1:7070".to_string());
+            maestro_tui::run(maestro_tui::RunConfig { daemon_url }).await?
+        }
     }
     Ok(())
 }