feat: phase 2 — am lab (benchmark N agents) + plugins d'événements (contrat JSON)

- #62: am lab --agents a,b --task <f> — séquentiel ou --parallel, capture
  durée/exit/sortie/coût estimé, rapport comparatif tableau + --json stable,
  tâches versionnables dans <state>/lab/ (--list), rejouables à l'identique
- #75: plugins/ sous state_dir, déclenchés sur on_install/on_start/on_stop/
  on_update (App::emit), contrat JSON stdin/stdout, timeout configurable,
  échec non bloquant, garde anti-récursion AM_PLUGINS_RUNNING, am plugins
  + am plugins --test <name> (CI), exemples notify + ci-webhook
- intégration REPL (parse, complétion, bannière, is_am_command), help, tips,
  man pages (am-lab.1, am-plugins.1), README, ROADMAP (26/27), v0.5.4
- 334 tests verts (309 + 25)

closes #62
closes #75

src/cli.rs

@@ -423,6 +423,10 @@ pub enum Command {
         #[arg(long, value_name = "NAME=VALUE")]
         var: Vec<String>,
     },
+    /// Benchmark: run the same task on several agents and compare (issue #62)
+    Lab(LabArgs),
+    /// List the event plugins and test one (issue #75)
+    Plugins(PluginsArgs),
     /// Show detailed information about one agent
     Info {
         /// Agent name or alias
@@ -570,6 +574,34 @@ pub struct ModelsArgs {
     pub days: Option<u64>,
 }
 
+/// Arguments of the lab command (issue #62).
+#[derive(Args, Debug, Clone, Default)]
+pub struct LabArgs {
+    /// Comma-separated agent names (or aliases) to benchmark
+    #[arg(long, value_name = "AGENTS", required_unless_present = "list")]
+    pub agents: Option<String>,
+    /// Task file (a bare name resolves under state_dir/lab/, .yaml appended)
+    #[arg(long, value_name = "FILE", required_unless_present = "list")]
+    pub task: Option<PathBuf>,
+    /// Run every agent concurrently instead of one after another
+    #[arg(long, action = ArgAction::SetTrue)]
+    pub parallel: bool,
+    /// Override the task timeout in seconds
+    #[arg(long, value_name = "SECS")]
+    pub timeout: Option<u64>,
+    /// List the task files of the lab directory
+    #[arg(long, action = ArgAction::SetTrue)]
+    pub list: bool,
+}
+
+/// Arguments of the plugins command (issue #75).
+#[derive(Args, Debug, Clone, Default)]
+pub struct PluginsArgs {
+    /// Run one plugin against a synthetic event and print its response
+    #[arg(long, value_name = "NAME")]
+    pub test: Option<String>,
+}
+
 /// Remote catalog subcommands (issues #60 #67).
 #[derive(Subcommand, Debug, Clone)]
 pub enum CatalogCmd {