feat: phase 2 — i18n messages EN/FR (--lang, AM_LANG/LANG, catalogue tr/tr_fmt, REPL lang) (closes #74)

tests/top_report_test.rs

@@ -45,6 +45,9 @@ fn report_md_contains_numbers_and_table() {
     ];
     let refs: Vec<&str> = lines.iter().map(|s| s.as_str()).collect();
     let app = app_with_events("report", &refs);
+    // Issue #74: the report follows the app language; force French so the
+    // assertions are deterministic whatever the host LANG says.
+    app.set_lang(agent_manager::i18n::Lang::Fr);
     let md = stats_cmd::report_md(&app, 7);
     assert!(md.contains("# Rapport agent-manager"), "md: {md}");
     assert!(md.contains("Lancements : 2"));