v0.1.27 release: Complete implementation

Features:
- Error logging system with ETHOS #1 compliance
- Command factory pattern with UUID generation
- Hardware binding with machine fingerprint validation
- Ed25519 cryptographic signing for updates
- Deduplication and idempotency for commands
- Circuit breakers and retry logic
- Frontend error logging integration

Bug Fixes:
- Version display using compile-time injection
- Migration 017 CONCURRENTLY issue resolved
- Docker build context fixes
- Rate limiting implementation verified

Documentation:
- README updated to reflect actual implementation
- v0.1.27 inventory analysis added

aggregator-server/internal/models/command.go

@@ -1,6 +1,7 @@
 package models
 
 import (
+	"errors"
 	"time"
 
 	"github.com/google/uuid"
@@ -16,12 +17,52 @@ type AgentCommand struct {
 	Source         string     `json:"source" db:"source"`
 	Signature      string     `json:"signature,omitempty" db:"signature"`
 	CreatedAt      time.Time  `json:"created_at" db:"created_at"`
+	UpdatedAt      time.Time  `json:"updated_at" db:"updated_at"`
 	SentAt         *time.Time `json:"sent_at,omitempty" db:"sent_at"`
 	CompletedAt    *time.Time `json:"completed_at,omitempty" db:"completed_at"`
 	Result         JSONB      `json:"result,omitempty" db:"result"`
 	RetriedFromID  *uuid.UUID `json:"retried_from_id,omitempty" db:"retried_from_id"`
 }
 
+// Validate checks if the command has all required fields
+func (c *AgentCommand) Validate() error {
+	if c.ID == uuid.Nil {
+		return ErrCommandIDRequired
+	}
+	if c.AgentID == uuid.Nil {
+		return ErrAgentIDRequired
+	}
+	if c.CommandType == "" {
+		return ErrCommandTypeRequired
+	}
+	if c.Status == "" {
+		return ErrStatusRequired
+	}
+	if c.Source != "manual" && c.Source != "system" {
+		return ErrInvalidSource
+	}
+	return nil
+}
+
+// IsTerminal returns true if the command is in a terminal state
+func (c *AgentCommand) IsTerminal() bool {
+	return c.Status == "completed" || c.Status == "failed" || c.Status == "cancelled"
+}
+
+// CanRetry returns true if the command can be retried
+func (c *AgentCommand) CanRetry() bool {
+	return c.Status == "failed" && c.RetriedFromID == nil
+}
+
+// Predefined errors for validation
+var (
+	ErrCommandIDRequired = errors.New("command ID cannot be zero UUID")
+	ErrAgentIDRequired   = errors.New("agent ID is required")
+	ErrCommandTypeRequired = errors.New("command type is required")
+	ErrStatusRequired    = errors.New("status is required")
+	ErrInvalidSource     = errors.New("source must be 'manual' or 'system'")
+)
+
 // CommandsResponse is returned when an agent checks in for commands
 type CommandsResponse struct {
 	Commands        []CommandItem        `json:"commands"`