feat: panel Timeline scatter (X=tiempo, Y=DAG, color=status) via ImPlot

- tabs.cpp draw_timeline: scatter ImPlot con eje X tiempo (UseLocalTime),
  eje Y categorico DAG (SetupAxisTicks), 1 serie por status con color
  consistente (verde/rojo/amarillo/gris).
- Combo ventana: 15m/1h/6h/24h/7d. Default 24h.
- Hover tooltip: punto mas cercano en pixel-space -> muestra status,
  dag, run id, started/finished, trigger, error.
- main.cpp: g_runs_all cache. Snapshot inicial via list_runs_http(limit=200)
  + upserts desde WS deltas. Auto-refresh por g_refresh_pending.
- Panel toggle "Timeline" en el menu View.
- Helper parse_rfc3339 inline (ignora offset, asume hora local — coherente
  con ImPlot::UseLocalTime).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

main.cpp

@@ -22,11 +22,23 @@ static std::string g_ws_path      = "/api/ws/dagruns";
 // Cache en memoria del primer fetch + ultimos eventos WS.
 static std::vector<dag_ui::DagInfo>  g_dags;
 static std::vector<dag_ui::DagRunRow> g_live_runs;     // upsert por id desde WS
+static std::vector<dag_ui::DagRunRow> g_runs_all;      // cache para Timeline (snapshot REST + WS upsert)
 static long long                     g_ws_runs_wm  = 0;
 static long long                     g_ws_steps_wm = 0;
 static int                           g_ws_msg_count = 0;
 static std::string                   g_last_error;
 
+// Upsert por id en g_runs_all. Mantiene mas reciente al frente.
+static void upsert_run_in_all(const dag_ui::DagRunRow& r) {
+    for (auto& existing : g_runs_all) {
+        if (existing.id == r.id) {
+            existing = r;
+            return;
+        }
+    }
+    g_runs_all.push_back(r);
+}
+
 static WsClient g_ws;
 
 // Toggles de paneles (visibles desde el menu View del menubar canonico)
@@ -35,6 +47,7 @@ static bool g_show_live       = true;
 static bool g_show_dag_list   = true;
 static bool g_show_dag_detail = true;
 static bool g_show_run_detail = true;
+static bool g_show_timeline   = true;
 
 // Auto-fetch DAG list una vez al arrancar.
 static bool g_initial_fetched = false;
@@ -75,6 +88,7 @@ static void parse_ws_payload(const std::string& payload) {
             r.finished_at = rj.value("finished_at", "");
             r.error       = rj.value("error", "");
             upsert_live_run(r);
+            upsert_run_in_all(r);
             // Cuando un run termina, refresca DAG List para que last_runs
             // refleje la nueva ejecucion en R1..R5.
             if (r.status == "success" || r.status == "failed" ||
@@ -139,6 +153,11 @@ static void render() {
         g_initial_fetched = true;
         g_refresh_pending = false;
         dag_ui::list_dags_http(g_api_url, g_dags);
+        // Tambien snapshot inicial / refresh de runs para Timeline.
+        std::vector<dag_ui::DagRunRow> tmp;
+        if (dag_ui::list_runs_http(g_api_url, "", 200, tmp)) {
+            for (auto& r : tmp) upsert_run_in_all(r);
+        }
     }
 
     // Drain WS messages this frame (cheap, max 64).
@@ -151,6 +170,7 @@ static void render() {
     if (g_show_dag_list)   dag_ui_tabs::draw_dag_list(g_api_url, g_dags, g_live_runs);
     if (g_show_dag_detail) dag_ui_tabs::draw_dag_detail(g_api_url);
     if (g_show_run_detail) dag_ui_tabs::draw_run_detail(g_api_url);
+    if (g_show_timeline)   dag_ui_tabs::draw_timeline(g_api_url, g_runs_all);
     if (g_show_main)       draw_main();
     if (g_show_live)       draw_live();
 }
@@ -163,6 +183,7 @@ int main(int /*argc*/, char** /*argv*/) {
         { "DAGs",        nullptr, &g_show_dag_list },
         { "DAG Detail",  nullptr, &g_show_dag_detail },
         { "Run Detail",  nullptr, &g_show_run_detail },
+        { "Timeline",    nullptr, &g_show_timeline },
         { "Live (WS)",   nullptr, &g_show_live },
         { "Main (diag)", nullptr, &g_show_main },
     };