feat: agent status dashboard with availability timeline and Gemini quota detection

- Detect Gemini TerminalQuotaError (daily quota) as BUDGET_EXCEEDED, not generic FAILED
- Surface container stderr tail in error so quota/rate-limit classifiers can match it
- Add agent_events table to persist rate-limit start/recovery events across restarts
- Add GET /api/agents/status endpoint returning live agent state + 24h event history
- Stats dashboard: agent status cards, 24h availability timeline, per-run execution table

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

2 files changed, 26 insertions, 0 deletions

diff --git a/internal/api/executions.go b/internal/api/executions.go
index 114425e..29af139 100644
--- a/internal/api/executions.go
+++ b/internal/api/executions.go
@@ -86,6 +86,31 @@ func (s *Server) handleGetExecutionLog(w http.ResponseWriter, r *http.Request) {
 	fmt.Fprint(w, content)
 }
 
+// handleGetAgentStatus returns the current status of all agents and recent rate-limit events.
+// GET /api/agents/status?since=<RFC3339>
+func (s *Server) handleGetAgentStatus(w http.ResponseWriter, r *http.Request) {
+	since := time.Now().Add(-24 * time.Hour)
+	if v := r.URL.Query().Get("since"); v != "" {
+		if t, err := time.Parse(time.RFC3339, v); err == nil {
+			since = t
+		}
+	}
+
+	events, err := s.store.ListAgentEvents(since)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		return
+	}
+	if events == nil {
+		events = []storage.AgentEvent{}
+	}
+
+	writeJSON(w, http.StatusOK, map[string]interface{}{
+		"agents": s.pool.AgentStatuses(),
+		"events": events,
+	})
+}
+
 // tailLogFile reads the last n lines from the file at path.
 func tailLogFile(path string, n int) (string, error) {
 	data, err := os.ReadFile(path)
diff --git a/internal/api/server.go b/internal/api/server.go
index e5d0ba6..2d5c308 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -121,6 +121,7 @@ func (s *Server) routes() {
 	s.mux.HandleFunc("GET /api/tasks/{id}/subtasks", s.handleListSubtasks)
 	s.mux.HandleFunc("GET /api/tasks/{id}/executions", s.handleListExecutions)
 	s.mux.HandleFunc("GET /api/executions", s.handleListRecentExecutions)
+	s.mux.HandleFunc("GET /api/agents/status", s.handleGetAgentStatus)
 	s.mux.HandleFunc("GET /api/executions/{id}", s.handleGetExecution)
 	s.mux.HandleFunc("GET /api/executions/{id}/log", s.handleGetExecutionLog)
 	s.mux.HandleFunc("GET /api/tasks/{id}/logs/stream", s.handleStreamTaskLogs)