v0.2.14 : aide Nushell, themes de couleurs et cadres blancs

- Aide facon Nushell : help <cmd>, <cmd> -h/--help, help, help commands,
  help --find <texte>, help <agent> (fiche info) - sections Usage/Flags/
  Command Type/Parameters/Input-output/Examples avec couleurs
- Commande version : tableau Nushell (commit, build, rustc, theme...) + --json ;
  build.rs pour commit/branche git ; -V reste la version courte
- Themes : --theme <nom> (default, ocean, sunset, forest, dracula, mono)
  + settings.theme dans la config ; activation VT Windows pour les couleurs
- Cadres blancs Nushell partages : list, search, status, doctor, ls/ps/
  where/get et menu d autocompletion Tab encadre (colonnes name/description)

src/app.rs

@@ -6,7 +6,8 @@ use crate::cli::Cli;
 use crate::config::{self, Config, Settings};
 use crate::output::Logger;
 use crate::state::StateStore;
-use anyhow::{Context, Result};
+use crate::theme::{self, Theme};
+use anyhow::{anyhow, Context, Result};
 use std::io::{IsTerminal, Write};
 use std::path::PathBuf;
 
@@ -19,6 +20,8 @@ pub struct App {
     pub catalog: Catalog,
     pub state: StateStore,
     pub log: Logger,
+    /// Active output color theme.
+    pub theme: &'static Theme,
 }
 
 #[derive(Debug, Clone)]
@@ -78,6 +81,7 @@ impl App {
             loaded.config.aliases.clone(),
             loaded.config.groups.clone(),
         );
+        let theme = resolve_theme(cli.theme.as_deref(), loaded.config.settings.theme.as_deref())?;
         Ok(Self {
             cli,
             config: loaded.config,
@@ -86,6 +90,7 @@ impl App {
             catalog,
             state,
             log,
+            theme,
         })
     }
 
@@ -105,6 +110,10 @@ impl App {
         !self.cli.no_color && std::io::stdout().is_terminal()
     }
 
+    pub fn theme(&self) -> &'static Theme {
+        self.theme
+    }
+
     /// Ask the user for confirmation on stderr. Accepts y/yes/o/oui.
     pub fn confirm(&self, question: &str) -> Result<bool> {
         if self.cli.yes {
@@ -119,6 +128,23 @@ impl App {
     }
 }
 
+/// Resolve the output color theme: the --theme flag wins, then the
+/// configuration entry, then the default theme. An unknown --theme value is
+/// an error; an unknown configured value silently falls back to the default.
+fn resolve_theme(flag: Option<&str>, configured: Option<&str>) -> Result<&'static Theme> {
+    if let Some(name) = flag {
+        return theme::find(name).ok_or_else(|| {
+            anyhow!(
+                "unknown theme '{name}' — available: {}",
+                theme::names().join(", ")
+            )
+        });
+    }
+    Ok(configured
+        .and_then(theme::find)
+        .unwrap_or_else(theme::default_theme))
+}
+
 /// Root directory for agent data (overridable with AGENT_MANAGER_DATA,
 /// mostly used by tests).
 pub fn data_dir() -> PathBuf {