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>

package.json

@@ -41,7 +41,8 @@
     "dev:api": "npm run dev --workspace @cloner/api",
     "dev:worker": "npm run dev --workspace @cloner/worker",
     "db:generate": "npm run generate --workspace @cloner/db",
-    "db:migrate": "npm run migrate --workspace @cloner/db"
+    "db:migrate": "npm run migrate --workspace @cloner/db",
+    "unpack": "node packages/cli/bin/ditto.mjs unpack"
   },
   "devDependencies": {
     "tsx": "4.22.4",