Add ditto unpack CLI to turn clone result JSON into a project tree

The REST API returns a clone as a giant `files` map JSON blob with no
first-party way to use it — users were left staring at kilobytes of
escaped JSON with no path from "you got JSON" to "here's a project".

Add packages/cli: a zero-dependency `ditto` CLI whose `unpack` command
walks the files{} map from POST /v1/clones (or GET .../result) and
writes a real project tree to disk:

- text files written from inline content;
- binary assets materialized from inline base64, else fetched from their
  reference URL using $DITTO_API_URL / $DITTO_API_KEY (--no-fetch writes
  just the text tree and lists skipped assets);
- path-traversal guards (clone results are untrusted) and sha256
  integrity checks;
- reads JSON from stdin ("-") so a curl response pipes straight in;
- clear errors for queued jobs with no files yet, and a tip pointing at
  the /bundle endpoint when assets can't be fetched.

Document the pipe-from-curl one-liner prominently next to the REST
examples in README.md and docs/SERVICE.md, add a package README, a
Repository Map row, a root `unpack` script, and a CHANGELOG entry.
Covered by 9 tests (text tree, stdin, inline base64, live URL fetch with
auth + relative-URL resolution, --no-fetch, traversal refusal, queued-job
detection, sha256 mismatch).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/cli/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "ditto",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Official ditto.site command-line helper: unpack a clone JSON result into a project tree on disk.",
+  "license": "MIT",
+  "author": "ion-design",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/ion-design/ditto.site.git",
+    "directory": "packages/cli"
+  },
+  "bugs": {
+    "url": "https://github.com/ion-design/ditto.site/issues"
+  },
+  "homepage": "https://github.com/ion-design/ditto.site#readme",
+  "type": "module",
+  "bin": {
+    "ditto": "./bin/ditto.mjs"
+  },
+  "files": [
+    "bin"
+  ],
+  "engines": {
+    "node": ">=20"
+  },
+  "scripts": {
+    "test": "node --test test/*.test.mjs"
+  }
+}