feat(dashboard): Add Polecat Workers section with activity monitoring

- Add FetchPolecats() to fetch tmux session data for active polecats
- Display polecat name, rig, activity status (green/yellow/red)
- Show status hint from last line of pane output
- Add FetchMergeQueue stub for interface compliance
- Update handler to pass polecats data to template
- Add Polecat Workers table section to convoy.html

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/web/handler_test.go

@@ -12,14 +12,24 @@ import (
 
 // MockConvoyFetcher is a mock implementation for testing.
 type MockConvoyFetcher struct {
-	Convoys []ConvoyRow
-	Error   error
+	Convoys    []ConvoyRow
+	MergeQueue []MergeQueueRow
+	Polecats   []PolecatRow
+	Error      error
 }
 
 func (m *MockConvoyFetcher) FetchConvoys() ([]ConvoyRow, error) {
 	return m.Convoys, m.Error
 }
 
+func (m *MockConvoyFetcher) FetchMergeQueue() ([]MergeQueueRow, error) {
+	return m.MergeQueue, nil
+}
+
+func (m *MockConvoyFetcher) FetchPolecats() ([]PolecatRow, error) {
+	return m.Polecats, nil
+}
+
 func TestConvoyHandler_RendersTemplate(t *testing.T) {
 	mock := &MockConvoyFetcher{
 		Convoys: []ConvoyRow{