feat(completion): unify shell wrappers behind task __complete

internal/complete/complete.go

@@ -0,0 +1,30 @@
+// Package complete implements the `task __complete` protocol consumed by the
+// shell completion wrappers. The protocol mirrors cobra v2 so a future
+// migration stays cheap.
+package complete
+
+import "os"
+
+const CommandName = "__complete"
+
+func IsActive() bool {
+	return len(os.Args) >= 2 && os.Args[1] == CommandName
+}
+
+// Directive mirrors cobra's ShellCompDirective bitfield.
+type Directive int
+
+const (
+	DirectiveDefault       Directive = 0
+	DirectiveError         Directive = 1 << 0
+	DirectiveNoSpace       Directive = 1 << 1
+	DirectiveNoFileComp    Directive = 1 << 2
+	DirectiveFilterFileExt Directive = 1 << 3
+	DirectiveFilterDirs    Directive = 1 << 4
+	DirectiveKeepOrder     Directive = 1 << 5
+)
+
+type Suggestion struct {
+	Value       string
+	Description string
+}