v6.2.0: deprecate Python deltaglider in favor of deltaglider_proxy (Rust) (#9)

The Rust `deltaglider_proxy` ships proxy + CLI + UI in one binary with a
byte-identical wire format. Maintaining both has been a duplication tax
(metadata-namespace fix v6.1.2 had to land twice). This release is the
final feature release; security/bug fixes stop here.

What this commit does:

- CLI: every invocation prints a deprecation notice to stderr pointing
  at github.com/beshu-tech/deltaglider_proxy with a one-line migration
  alias (`alias dg='deltaglider_proxy s3'`). Banner prints once per
  process; suppress via DG_SUPPRESS_DEPRECATION=1 for CI that hasn't
  migrated yet.
- README: prominent deprecation banner at the top with the migration
  command and the archive-timing notice (~1 week after v6.2.0 ships).
- pyproject.toml: description prefixed with "DEPRECATED" so PyPI search
  results show the warning. Classifier moved Beta -> Inactive.
- CHANGELOG: v6.2.0 entry under "Deprecated" documenting the migration
  path + archive plan, preserving the carried-forward Fixed/Changed/
  Added items from Unreleased.

Repo archive timing: Maintainer will archive ~1 week after v6.2.0 hits
PyPI to give users a window to see the stderr notice on their next
update. PyPI installs continue to work indefinitely.

No behaviour changes to the wire format, the CLI surface, or the
metadata schema. Existing buckets remain readable forever.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -5,9 +5,39 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [Unreleased]
+## [6.2.0] - 2026-05-22 — Final release; project deprecated
 
-### Fixed
+### Deprecated
+- **The `deltaglider` Python package is deprecated as of this release.**
+  The canonical implementation is now
+  [`deltaglider_proxy`](https://github.com/beshu-tech/deltaglider_proxy), a
+  single Rust binary that ships the S3-compatible proxy, the `s3` CLI
+  (every Python subcommand has a 1:1 Rust equivalent), and the web UI.
+  Wire format is byte-identical: data written by this tool is readable
+  by `deltaglider_proxy` and vice versa.
+- **Every CLI invocation now prints a deprecation banner to stderr.**
+  Set `DG_SUPPRESS_DEPRECATION=1` to silence it for CI/automation that
+  hasn't migrated yet.
+- **PyPI classifier bumped to `Development Status :: 7 - Inactive`.**
+- **Repo will be archived approximately one week after this release.**
+  PyPI installs continue to work indefinitely (PyPI never deletes
+  published versions), but no further updates or security fixes will
+  land. File new issues against
+  [`deltaglider_proxy`](https://github.com/beshu-tech/deltaglider_proxy/issues).
+
+Migration:
+```bash
+brew install beshu-tech/tap/deltaglider_proxy
+# or grab a binary from
+# https://github.com/beshu-tech/deltaglider_proxy/releases
+
+alias dg='deltaglider_proxy s3'
+dg cp foo s3://bucket/foo
+dg ls s3://bucket
+dg migrate s3://src s3://dest
+```
+
+### Fixed (carried from Unreleased)
 - **Direct-upload metadata now uses the canonical `dg-*` dashed namespace.** Pre-fix, files routed through `_upload_direct` (non-delta-eligible extensions: `.sha1`, `.sha512`, etc.) wrote metadata with bare underscored keys (`original_name`, `file_sha256`, `compression`) while delta and reference uploads correctly used the namespaced form (`dg-original-name`, `dg-file-sha256`, `dg-compression`). Downstream consumers — most visibly the [DeltaGlider Proxy](https://github.com/beshu-tech/deltaglider_proxy) — only recognised the dashed form, so every `.sha1`/`.sha512` listing triggered a `PATHOLOGICAL | Missing/corrupt DG metadata` warning. Aligned the writer to the canonical scheme so new uploads stop producing log spam.
 
 ### Changed