feat(command): improve slash command UX

Make slash commands easier to navigate in chat by splitting help into levels, compacting list output, and surfacing current selections for model, search, memory, and browser settings. Also route /status to the active conversation session and add an access inspector so users can understand their current command and ACL context.

internal/command/parser_test.go

@@ -13,6 +13,8 @@ func TestParse_Basic(t *testing.T) {
 		args     []string
 	}{
 		{"/help", "help", "", nil},
+		{"/help model", "help", "model", nil},
+		{"/help model set", "help", "model", []string{"set"}},
 		{"/subagent list", "subagent", "list", nil},
 		{"/subagent get mybot", "subagent", "get", []string{"mybot"}},
 		{"/schedule create daily \"0 9 * * *\" Send report", "schedule", "create", []string{"daily", "0 9 * * *", "Send", "report"}},