fix(agent): respect --session flag value when routing messages (#1039)

When starting the interactive agent with --session <name>, the provided
session key was being ignored during routing. The router always fell back
to 'agent:main:main' because plain names (without a colon) were not
recognized as valid session keys.

Root cause: the session key passed via --session flag (e.g. 'foobar') had
no namespace prefix, so the routing logic treated it as unresolvable and
defaulted to the hardcoded 'agent:main:main' session, causing all
conversation history to accumulate in agent_main_main.json regardless of
the --session value.

Fix: before routing, check if the session key contains a colon; if not,
prefix it with 'agent:main:' so that '--session foobar' correctly resolves
to 'agent:main:foobar' and the session file is created as expected.

cmd/picoclaw/internal/agent/helpers.go

@@ -10,7 +10,6 @@ import (
 	"strings"
 
 	"github.com/chzyer/readline"
-
 	"github.com/sipeed/picoclaw/cmd/picoclaw/internal"
 	"github.com/sipeed/picoclaw/pkg/agent"
 	"github.com/sipeed/picoclaw/pkg/bus"
@@ -23,6 +22,11 @@ func agentCmd(message, sessionKey, model string, debug bool) error {
 		sessionKey = "cli:default"
 	}
 
+	// If the user provides a plain name (no colon), treat it as a session label
+	if !strings.Contains(sessionKey, ":") {
+		sessionKey = fmt.Sprintf("agent:main:%s", sessionKey)
+	}
+
 	if debug {
 		logger.SetLevel(logger.DEBUG)
 		fmt.Println("🔍 Debug mode enabled")