feat(maestro-tui): wire --config flag + document tui in INSTALL.md (NAP-283)

- `RunConfig` grows a `config_path: Option<PathBuf>` field, plumbed from the
  umbrella binary's global `--config` flag through to `MaestroConfigFile`
  loading. Explicit `--config <path>` wins over `$MAESTRO_CONFIG` over the
  platform default; a missing file still falls back to shipped defaults.
- `docs/INSTALL.md` gains a "terminal UI" section: that `maestro tui` ships
  in the default feature set, how to opt out (`--no-default-features
  --features cli,daemon`), the `MAESTRO_DAEMON_URL` override, and a worked
  example of `[tui]` / `[tui.keymap.normal]` config pointing at the
  full action vocabulary in the design spec.
- Adds a thin-build line for `--features cli` (CLI-only client) and lists
  `tui` in the default-feature set.
- CLAUDE.md repo-layout block lists the new `maestro-tui` crate.

Closes the NAP-275 v1 epic.

crates/maestro-tui/src/lib.rs

@@ -22,6 +22,7 @@ pub mod state;
 pub mod tabs;
 pub mod terminal;
 
+use std::path::PathBuf;
 use std::time::Duration;
 
 use ratatui::backend::CrosstermBackend;
@@ -38,6 +39,10 @@ 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,
+    /// Explicit `--config <path>` override from the umbrella binary's global
+    /// flag. When `None`, [`maestro_config::resolve_config_path`] picks the
+    /// default (`$MAESTRO_CONFIG` or `~/.config/maestro/config.toml`).
+    pub config_path: Option<PathBuf>,
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -62,8 +67,13 @@ pub async fn run(cfg: RunConfig) -> Result<(), TuiError> {
     // Health check — fail fast if no daemon is reachable.
     health_check(&base_url).await?;
 
-    // Load runtime config from disk if present; fall back to defaults.
-    let cfg_file = match maestro_config::resolve_config_path() {
+    // Load runtime config: explicit `--config <path>` wins, then
+    // `$MAESTRO_CONFIG`, then the platform default. Missing file is fine —
+    // we fall back to shipped defaults.
+    let cfg_path = cfg.config_path.clone().map(Ok).unwrap_or_else(|| {
+        maestro_config::resolve_config_path().map_err(|e| TuiError::Config(e.to_string()))
+    });
+    let cfg_file = match cfg_path {
         Ok(path) => maestro_config::MaestroConfigFile::load_or_default(&path)
             .map_err(|e| TuiError::Config(e.to_string()))?,
         Err(_) => maestro_config::MaestroConfigFile::default(),

crates/maestro/src/main.rs

@@ -167,7 +167,11 @@ async fn dispatch(cli: Cli) -> Result<(), Box<dyn std::error::Error>> {
             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?
+            maestro_tui::run(maestro_tui::RunConfig {
+                daemon_url,
+                config_path: cli.config,
+            })
+            .await?
         }
     }
     Ok(())