feat: add bubbletea TUI dashboard for bot server management

Implementa un dashboard interactivo con bubbletea siguiendo el patrón
pure core / impure shell del proyecto:

- pkg/tui/ (PURE): Model, Update, View — solo fmt y strings, cero I/O.
  Update produce Intent[] (datos puros) en vez de side effects.
- shell/tui/ (IMPURE): Adapter convierte Intent[] en tea.Cmd[] con I/O real
  (process management, /proc stats, log tail).
- cmd/dashboard/ (composición): Bridge conecta pure Update con shell Adapter
  usando la Elm Architecture de bubbletea.

Pantallas: Main Menu → Agent List → Agent Actions (start/stop/restart/kill) → Logs.
Navegación: flechas ↑↓, Enter seleccionar, 0 volver, q salir.

Dependencias añadidas: bubbletea, lipgloss.
Actualiza .gitignore para anclar binarios a raíz (/agentctl, /dashboard).
Documenta nuevos scripts en CLAUDE.md.

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

pkg/tui/messages.go

@@ -0,0 +1,20 @@
+package tui
+
+// Messages are pure data returned by the shell adapter.
+// They carry the result of an I/O operation back into the pure Update.
+
+// MsgAgentsLoaded carries refreshed agent data.
+type MsgAgentsLoaded struct{ Agents []AgentView }
+
+// MsgActionDone reports the result of an agent action (start/stop/kill/restart).
+type MsgActionDone struct {
+	AgentID string
+	Action  string
+	Err     error
+}
+
+// MsgLogsLoaded carries log lines for the selected agent.
+type MsgLogsLoaded struct{ Lines []string }
+
+// MsgTick triggers a periodic refresh.
+type MsgTick struct{}