feat(tui): declarative keymap + command registry

crates/owlen-core/src/config.rs

@@ -1584,6 +1584,8 @@ pub struct UiSettings {
     pub show_timestamps: bool,
     #[serde(default = "UiSettings::default_icon_mode")]
     pub icon_mode: IconMode,
+    #[serde(default)]
+    pub keymap_path: Option<String>,
 }
 
 /// Preference for which symbol set to render in the terminal UI.
@@ -1721,6 +1723,7 @@ impl Default for UiSettings {
             render_markdown: Self::default_render_markdown(),
             show_timestamps: Self::default_show_timestamps(),
             icon_mode: Self::default_icon_mode(),
+            keymap_path: None,
         }
     }
 }