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>

1 files changed, 63 insertions, 0 deletions

diff --git a/internal/storage/db.go b/internal/storage/db.go
index 8bc9864..0d11b4e 100644
--- a/internal/storage/db.go
+++ b/internal/storage/db.go
@@ -99,6 +99,16 @@ func (s *DB) migrate() error {
 			key TEXT PRIMARY KEY,
 			value TEXT NOT NULL
 		)`,
+		`CREATE TABLE IF NOT EXISTS agent_events (
+			id TEXT PRIMARY KEY,
+			agent TEXT NOT NULL,
+			event TEXT NOT NULL,
+			timestamp DATETIME NOT NULL,
+			until DATETIME,
+			reason TEXT
+		)`,
+		`CREATE INDEX IF NOT EXISTS idx_agent_events_agent ON agent_events(agent)`,
+		`CREATE INDEX IF NOT EXISTS idx_agent_events_timestamp ON agent_events(timestamp)`,
 	}
 	for _, m := range migrations {
 		if _, err := s.db.Exec(m); err != nil {
@@ -858,3 +868,56 @@ func (s *DB) SetSetting(key, value string) error {
 	_, err := s.db.Exec(`INSERT INTO settings (key, value) VALUES (?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value`, key, value)
 	return err
 }
+
+// AgentEvent records a rate-limit state change for an agent.
+type AgentEvent struct {
+	ID        string
+	Agent     string
+	Event     string     // "rate_limited" | "available"
+	Timestamp time.Time
+	Until     *time.Time // non-nil for "rate_limited" events
+	Reason    string     // "transient" | "quota"
+}
+
+// RecordAgentEvent inserts an agent rate-limit event.
+func (s *DB) RecordAgentEvent(e AgentEvent) error {
+	_, err := s.db.Exec(
+		`INSERT INTO agent_events (id, agent, event, timestamp, until, reason) VALUES (?, ?, ?, ?, ?, ?)`,
+		e.ID, e.Agent, e.Event, e.Timestamp.UTC(), timeOrNull(e.Until), e.Reason,
+	)
+	return err
+}
+
+// ListAgentEvents returns agent events since the given time, newest first.
+func (s *DB) ListAgentEvents(since time.Time) ([]AgentEvent, error) {
+	rows, err := s.db.Query(
+		`SELECT id, agent, event, timestamp, until, reason FROM agent_events WHERE timestamp >= ? ORDER BY timestamp DESC LIMIT 500`,
+		since.UTC(),
+	)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var events []AgentEvent
+	for rows.Next() {
+		var e AgentEvent
+		var until sql.NullTime
+		var reason sql.NullString
+		if err := rows.Scan(&e.ID, &e.Agent, &e.Event, &e.Timestamp, &until, &reason); err != nil {
+			return nil, err
+		}
+		if until.Valid {
+			e.Until = &until.Time
+		}
+		e.Reason = reason.String
+		events = append(events, e)
+	}
+	return events, rows.Err()
+}
+
+func timeOrNull(t *time.Time) interface{} {
+	if t == nil {
+		return nil
+	}
+	return t.UTC()
+}