fix(crossfile): add built-in subagent whitelist to prevent false positives

Added builtInSubagentTypes map to exclude Claude Code runtime subagents
(general-purpose, Explore, Plan, etc.) from "missing agent" validation.
These agents exist in the runtime, not as user files.

Author: Test User

internal/cli/crossfile.go

@@ -9,6 +9,16 @@ import (
 	"github.com/dotcommander/cclint/internal/discovery"
 )
 
+// builtInSubagentTypes are Task() targets that exist in Claude Code's runtime,
+// not as user-defined agent files. These should not trigger "missing agent" errors.
+var builtInSubagentTypes = map[string]bool{
+	"general-purpose":   true,
+	"statusline-setup":  true,
+	"Explore":           true,
+	"Plan":              true,
+	"claude-code-guide": true,
+}
+
 // CrossFileValidator validates references between components
 type CrossFileValidator struct {
 	agents   map[string]discovery.File
@@ -72,6 +82,11 @@ func (v *CrossFileValidator) ValidateCommand(filePath string, contents string, f
 			continue
 		}
 
+		// Skip built-in subagent types (they exist in runtime, not as files)
+		if builtInSubagentTypes[agentRef] {
+			continue
+		}
+
 		// Check if agent exists - OUR OBSERVATION (consistency check)
 		if _, exists := v.agents[agentRef]; !exists {
 			seenAgentErrors[agentRef] = true