Step 30: Targeting CLI commands.

tag add/remove/list for machine-local tags. identity prints full label
set. --only/--never flags on add. target command to set/clear targeting
on existing entries. SetTargeting garden method.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

garden/target.go

@@ -0,0 +1,34 @@
+package garden
+
+import "fmt"
+
+// SetTargeting updates the Only/Never fields on an existing manifest entry.
+// If clear is true, both fields are reset to nil.
+func (g *Garden) SetTargeting(path string, only, never []string, clear bool) error {
+	abs, err := ExpandTildePath(path)
+	if err != nil {
+		return fmt.Errorf("expanding path: %w", err)
+	}
+	tilded := toTildePath(abs)
+
+	entry := g.findEntry(tilded)
+	if entry == nil {
+		return fmt.Errorf("not tracking %s", tilded)
+	}
+
+	if clear {
+		entry.Only = nil
+		entry.Never = nil
+	} else {
+		if len(only) > 0 {
+			entry.Only = only
+			entry.Never = nil
+		}
+		if len(never) > 0 {
+			entry.Never = never
+			entry.Only = nil
+		}
+	}
+
+	return g.manifest.Save(g.manifestPath)
+}