sessions : am sessions --resume <id> (issue #32) - relance en arriere-plan avec les arguments et le cwd d'origine, cwd optionnel dans spawn_background, gardes running/repl/erreurs claires

src/commands/sessions_cmd.rs

@@ -44,10 +44,14 @@ pub fn run(
     project: Option<&str>,
     status: Option<&str>,
     show: Option<&str>,
+    resume: Option<&str>,
 ) -> Result<i32> {
     if let Some(id) = show {
         return show_one(app, id);
     }
+    if let Some(id) = resume {
+        return resume_session(app, id);
+    }
     sessions::reconcile(app)?;
     let sf = sessions::load(app)?;
     let mut rows: Vec<SessionRow> = sf
@@ -130,6 +134,48 @@ fn show_one(app: &App, id: &str) -> Result<i32> {
     Ok(0)
 }
 
+/// Resume a finished session: relaunch the agent in the background with
+/// its recorded arguments and working directory (issue #32).
+fn resume_session(app: &App, id: &str) -> Result<i32> {
+    sessions::reconcile(app)?;
+    let sf = sessions::load(app)?;
+    let Some(r) = sf.sessions.get(id).cloned() else {
+        bail!("unknown session '{id}' — 'am sessions' lists every session");
+    };
+    if r.kind != "agent" {
+        bail!("session '{id}' is a REPL session — start it again with 'am'");
+    }
+    if r.status == "running" {
+        app.log.info(&format!("session '{id}' is still running"));
+        return Ok(0);
+    }
+    let Some(agent_name) = r.agent.clone() else {
+        bail!("session '{id}' has no agent");
+    };
+    require_agent(app, &agent_name)?;
+    if app.dry_run() {
+        app.log.dry(format!(
+            "would resume session {id}: start {} --background with {} arg(s)",
+            agent_name,
+            r.args.len()
+        ));
+        return Ok(0);
+    }
+    let cwd = r.cwd.as_deref().map(std::path::Path::new);
+    let opts = crate::cli::StartArgs {
+        agent: Some(agent_name.clone()),
+        background: true,
+        args: r.args.clone(),
+        ..Default::default()
+    };
+    app.log.info(&format!(
+        "resuming session {id}: {} ({} arg(s))",
+        agent_name,
+        r.args.len()
+    ));
+    crate::commands::run_cmd::start_with_cwd(app, &opts, cwd)
+}
+
 /// "20260815_143926_a1b2c3" -> "20260815_143926"
 fn short_id(id: &str) -> String {
     id.chars().take(15).collect()