feat: e opens a repo's SOPS or .env file, in nvim, sops edit or your editor

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

internal/provider/provider.go

@@ -169,3 +169,18 @@ type Current interface {
 type Locator interface {
 	Locate(ctx context.Context, address string) (sourceID string, ok bool, err error)
 }
+
+// Files is implemented by providers whose containers are files on disk
+// (SOPS and .env files in repos), so they can be opened in an editor.
+type Files interface {
+	// File is where c is, and for o (nil for the whole file) the line its
+	// key is on.
+	File(c Container, o *Object) (File, error)
+}
+
+// File is a container's file, to open.
+type File struct {
+	Path string
+	Line int    // 1-based; 0 for the top
+	Sops string // the sops command to edit it with; empty for a plain file
+}