docs: serve api-catalog by enabling download-spec (#890)

* docs: serve api-catalog by enabling download-spec

The docs site advertises </.well-known/api-catalog>; rel="api-catalog"
in its Link header, but that path returns 404 because no OpenAPI
download is configured.

Adding "download-spec" to contextual.options makes Mintlify publish the
RFC 9727 linkset at /.well-known/api-catalog, linking each OpenAPI spec
declared in docs.json (including the OpenHands Cloud spec) so agents can
discover the API.

Co-authored-by: openhands <openhands@all-hands.dev>

* docs: exclude legacy V0 spec from api-catalog

The legacy V0_openapi.json is unreferenced in docs.json but Mintlify
auto-uploads every OpenAPI spec in the repo, so enabling download-spec
advertised it in the /.well-known/api-catalog linkset alongside the two
current specs. Add a .mintignore entry to exclude it from publishing.

Co-authored-by: openhands <openhands@all-hands.dev>

---------

Co-authored-by: openhands <openhands@all-hands.dev>
Co-authored-by: enyst <engel.nyst@gmail.com>

Author: 3 people

.mintignore

@@ -0,0 +1,5 @@
+# Legacy OpenHands V0 REST API schema. Superseded by the Cloud schema
+# (openapi/openhands-cloud.json) and kept only for historical reference.
+# Excluded so it is not published, indexed, or advertised in the
+# /.well-known/api-catalog linkset.
+openapi/V0_openapi.json

docs.json

@@ -702,6 +702,7 @@
     "options": [
       "copy",
       "view",
+      "download-spec",
       "chatgpt",
       "claude"
     ]