Add passv: a Vault-backed drop-in for pass

Provide a password-store CLI that keeps pass's on-disk layout (<name>.gpg
binary OpenPGP under $PASSWORD_STORE_DIR) but routes all encryption and
decryption through a vault-plugin-secrets-gpg engine mount, so the GPG private
key never lives on the client.

- Implement init/show/ls/insert/generate/edit/rm/mv/cp/find/grep/git with
  pass-compatible flags and implicit `passv <name>`=show dispatch.
- Resolve the recipient from a Vault ref: .gpg-id holds <mount>/<key> for
  passv-native stores, or a sibling .vault-id lets a store keep real GPG
  fingerprints in .gpg-id for dual gpg+Vault use.
- mv/cp re-encrypt across differing recipients; same-recipient moves copy the
  ciphertext verbatim.
- Ship the sibling build/packaging/CI: nfpm RPM to /usr/bin/passv (artifactapi
  rpm-internal on v* tag), Woodpecker PR/release pipelines, unit tests plus a
  real-Vault e2e that also proves dual gpg+Vault decryption.
- README covers store creation, migrating a GPG pass store, and dual-mode.

tree.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// printTree renders the entry tree under sub in the same shape pass does (via
+// `tree`): directories and entries sorted together, `.gpg` suffixes stripped,
+// dotfiles hidden.
+func printTree(s *store, sub string) error {
+	root := filepath.Join(s.dir, sub)
+	if fi, err := os.Stat(root); err != nil || !fi.IsDir() {
+		return errf("Error: %s is not in the password store.", sub)
+	}
+	if sub == "" {
+		fmt.Println("Password Store")
+	} else {
+		fmt.Println(sub)
+	}
+	return printBranch(root, "")
+}
+
+func printBranch(dir, prefix string) error {
+	ents, err := os.ReadDir(dir)
+	if err != nil {
+		return err
+	}
+
+	var items []os.DirEntry
+	for _, e := range ents {
+		if strings.HasPrefix(e.Name(), ".") {
+			continue
+		}
+		if !e.IsDir() && !strings.HasSuffix(e.Name(), ".gpg") {
+			continue
+		}
+		items = append(items, e)
+	}
+	sort.Slice(items, func(i, j int) bool { return items[i].Name() < items[j].Name() })
+
+	for i, e := range items {
+		last := i == len(items)-1
+		branch, extend := "├── ", "│   "
+		if last {
+			branch, extend = "└── ", "    "
+		}
+		name := e.Name()
+		if !e.IsDir() {
+			name = strings.TrimSuffix(name, ".gpg")
+		}
+		fmt.Println(prefix + branch + name)
+		if e.IsDir() {
+			if err := printBranch(filepath.Join(dir, e.Name()), prefix+extend); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}