feat: Add --args flag for natural language executor instructions (gt-1py3y)

- Add Args field to SlungWork struct in wisp/types.go
- Add --args/-a flag to gt sling command
- Display args in gt prime autonomous mode
- Display args in gt mol status output

The --args string is stored in the hook and shown to the LLM executor,
which interprets the instructions naturally without schema maintenance.

Example: gt sling beads-release --args "patch release"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/prime.go

@@ -1360,6 +1360,11 @@ func checkSlungWork(ctx RoleContext) bool {
 	if sw.Context != "" {
 		fmt.Printf("  Context: %s\n", sw.Context)
 	}
+	if sw.Args != "" {
+		fmt.Printf("  Args: %s\n", style.Bold.Render(sw.Args))
+		fmt.Println()
+		fmt.Printf("  %s Use these args to guide your execution.\n", style.Bold.Render("→"))
+	}
 	fmt.Printf("  Slung by: %s at %s\n", sw.CreatedBy, sw.CreatedAt.Format("2006-01-02 15:04:05"))
 	fmt.Println()