feat: añadir sistema de comandos directos (!command)

Implementa pkg/command/ como core puro: tipos Spec/ParsedArgs, parser de
args key=value con soporte de comillas, specs de 8 comandos built-in
(help, tools, tool, ping, status, info, clear, version) y BuiltinNames()
para aliases.

En agents/runtime.go: nuevo flujo handleEvent que prioriza comandos sobre
LLM — custom rules del agente → built-in handlers → comando desconocido →
LLM fallback. Handlers en agents/commands.go. El comando !tool ejecuta
tools directamente via Registry con args key=value parseados.

LLM ahora es opcional: si no hay provider configurado, el agente corre
como simple_bot respondiendo solo a comandos.

Se extrae executeActions() como helper reutilizable para ambos flujos
(comando y no-comando).

pkg/command/parse.go

@@ -0,0 +1,91 @@
+package command
+
+import (
+	"encoding/json"
+	"strings"
+)
+
+// ParseArgs converts a slice of raw arguments into structured ParsedArgs.
+// Supports: positional args, key=value pairs, and quoted values like key="hello world".
+// Pure function — no side effects.
+func ParseArgs(args []string) ParsedArgs {
+	p := ParsedArgs{
+		Named: make(map[string]string),
+		Raw:   args,
+	}
+
+	// First, rejoin args to handle quoted values that were split by Fields().
+	joined := strings.Join(args, " ")
+	tokens := tokenize(joined)
+
+	for _, tok := range tokens {
+		if idx := strings.IndexByte(tok, '='); idx > 0 {
+			key := tok[:idx]
+			val := tok[idx+1:]
+			// Strip surrounding quotes from value
+			val = stripQuotes(val)
+			p.Named[key] = val
+		} else {
+			p.Positional = append(p.Positional, tok)
+		}
+	}
+
+	return p
+}
+
+// ArgsToJSON converts a named args map to a JSON string for tools.Registry.Execute.
+// Pure function.
+func ArgsToJSON(named map[string]string) string {
+	if len(named) == 0 {
+		return ""
+	}
+	m := make(map[string]any, len(named))
+	for k, v := range named {
+		m[k] = v
+	}
+	b, _ := json.Marshal(m)
+	return string(b)
+}
+
+// tokenize splits a string respecting quoted values.
+// e.g. `host=server1 command="uptime -a"` → ["host=server1", `command="uptime -a"`]
+func tokenize(s string) []string {
+	var tokens []string
+	var current strings.Builder
+	inQuote := false
+	quoteChar := byte(0)
+
+	for i := 0; i < len(s); i++ {
+		ch := s[i]
+		switch {
+		case !inQuote && (ch == '"' || ch == '\''):
+			inQuote = true
+			quoteChar = ch
+			current.WriteByte(ch)
+		case inQuote && ch == quoteChar:
+			inQuote = false
+			current.WriteByte(ch)
+		case !inQuote && ch == ' ':
+			if current.Len() > 0 {
+				tokens = append(tokens, current.String())
+				current.Reset()
+			}
+		default:
+			current.WriteByte(ch)
+		}
+	}
+	if current.Len() > 0 {
+		tokens = append(tokens, current.String())
+	}
+	return tokens
+}
+
+// stripQuotes removes surrounding double or single quotes from a string.
+func stripQuotes(s string) string {
+	if len(s) >= 2 {
+		if (s[0] == '"' && s[len(s)-1] == '"') || (s[0] == '\'' && s[len(s)-1] == '\'') {
+			return s[1 : len(s)-1]
+		}
+	}
+	return s
+}