feat: implement ControlTower TUI for cluster and host monitoring

Add complete TUI application for monitoring Kubernetes clusters and host
systems. Features include:

Core features:
- Collector framework with concurrent scheduling
- Host collectors: disk, memory, load, network
- Kubernetes collectors: pods, nodes, workloads, events with informers
- Issue deduplication, state management, and resolve-after logic
- Bubble Tea TUI with table view, details pane, and filtering
- JSON export functionality

UX improvements:
- Help overlay with keybindings
- Priority/category filters with visual indicators
- Direct priority jump (0/1/2/3)
- Bulk acknowledge (Shift+A)
- Clipboard copy (y)
- Theme toggle (T)
- Age format toggle (d)
- Wide title toggle (t)
- Vi-style navigation (j/k)
- Home/End jump (g/G)
- Rollup drill-down in details

Robustness:
- Grace period for unreachable clusters
- Rollups for high-volume issues
- Flap suppression
- RBAC error handling

Files: All core application code with tests for host collectors,
engine, store, model, and export packages.

internal/collectors/k8s/issues_events.go

@@ -0,0 +1,101 @@
+package k8s
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	corev1 "k8s.io/api/core/v1"
+
+	"tower/internal/model"
+)
+
+var warningEventReasons = map[string]struct{}{
+	"FailedScheduling": {},
+	"FailedMount":      {},
+	"BackOff":          {},
+	"Unhealthy":        {},
+	"OOMKilling":       {},
+	"FailedPull":       {},
+	"Forbidden":        {},
+	"ErrImagePull":     {},
+	"ImagePullBackOff": {},
+}
+
+// IssuesFromEvents applies the PLAN.md Event rules.
+//
+// Dedup by (object UID, reason). For v1 Events, this is approximated by
+// (involvedObject.uid, reason).
+func IssuesFromEvents(events []*corev1.Event, now time.Time) []model.Issue {
+	_ = now
+	out := make([]model.Issue, 0, 16)
+	seen := map[string]struct{}{}
+
+	for _, e := range events {
+		if e == nil {
+			continue
+		}
+		if strings.ToLower(e.Type) != strings.ToLower(string(corev1.EventTypeWarning)) {
+			continue
+		}
+		if _, ok := warningEventReasons[e.Reason]; !ok {
+			continue
+		}
+
+		uid := string(e.InvolvedObject.UID)
+		k := uid + ":" + e.Reason
+		if _, ok := seen[k]; ok {
+			continue
+		}
+		seen[k] = struct{}{}
+
+		ns := e.InvolvedObject.Namespace
+		if ns == "" {
+			ns = e.Namespace
+		}
+
+		objKey := e.InvolvedObject.Kind + "/" + e.InvolvedObject.Name
+		title := fmt.Sprintf("K8s Event %s: %s (%s)", e.Reason, objKey, ns)
+		if ns == "" {
+			title = fmt.Sprintf("K8s Event %s: %s", e.Reason, objKey)
+		}
+
+		details := strings.TrimSpace(e.Message)
+		if details == "" {
+			details = "Warning event emitted by Kubernetes."
+		}
+
+		out = append(out, model.Issue{
+			ID:       fmt.Sprintf("k8s:event:%s:%s", uid, e.Reason),
+			Category: model.CategoryKubernetes,
+			Priority: model.PriorityP2,
+			Title:    title,
+			Details:  details,
+			Evidence: map[string]string{
+				"kind":      e.InvolvedObject.Kind,
+				"reason":    e.Reason,
+				"namespace": ns,
+				"name":      e.InvolvedObject.Name,
+				"uid":       uid,
+			},
+			SuggestedFix: suggestedFixForEvent(ns, e.InvolvedObject.Kind, e.InvolvedObject.Name),
+		})
+	}
+
+	return out
+}
+
+func suggestedFixForEvent(ns, kind, name string) string {
+	kindLower := strings.ToLower(kind)
+	if ns != "" {
+		switch kindLower {
+		case "pod":
+			return fmt.Sprintf("kubectl -n %s describe pod %s", ns, name)
+		case "node":
+			return fmt.Sprintf("kubectl describe node %s", name)
+		default:
+			return fmt.Sprintf("kubectl -n %s describe %s %s", ns, kindLower, name)
+		}
+	}
+	return fmt.Sprintf("kubectl describe %s %s", kindLower, name)
+}