feat: implement --show-metadata option

CHANGELOG.md

@@ -7,6 +7,34 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [development]
 
+### Added
+
+**Core engine**
+
+- **Unified worker pool** — single protocol-agnostic worker pool (`internal/pool`)
+  used by FTP, SFTP, and WebDAV recursive-parallel downloads. Replaces three
+  near-identical semaphore+WaitGroup implementations with a shared, tested
+  concurrency primitive.
+- **Graceful shutdown on SIGINT** — persist `.goget.meta` sidecar on interrupt
+  for SFTP single-file downloads, ensuring progress is saved for resume.
+
+**Recursive downloading & mirroring**
+
+- `--adjust-extension` extended to non-HTTP protocols — applies `.html`
+  extension to `text/html` files downloaded via Gopher and WebDAV.
+- `--backup-converted` — keep `.orig` backups of files before link conversion
+  during recursive mirroring. Previously only available for HTTP/HTTPS;
+  now works for WebDAV mirrors too.
+
+**Download management**
+
+- `--show-metadata` — displays `.goget.meta` sidecar contents for debugging
+  interrupted / resumed downloads. Accepts a path to the downloaded output
+  (the sidecar is located next to it) or a direct path to the sidecar file.
+  Renders a human-readable summary by default and switches to raw JSON
+  output when combined with `--json`. Credentials embedded in the stored
+  URL are masked before display (the password placeholder is `xxxxx`).
+
 ## [1.0.0] — 2026-06-26
 
 First public release: a modern IPv6-first command-line download utility built on