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`.

Cargo.toml

@@ -19,6 +19,7 @@ jsonwebtoken = { version = "9", default-features = false }
 libc = "0.2"
 maestro-config = { path = "crates/maestro-config" }
 maestro-protocol = { path = "crates/maestro-protocol" }
+maestro-tui = { path = "crates/maestro-tui" }
 nix = { version = "0.29", default-features = false, features = ["term", "signal"] }
 rand = "0.8"
 reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls", "cookies", "stream"] }