RayRAG v0.10.1 — HTTP status and business code, separated as documented

RayRAG v0.10.1

The business-code contract from the API guide

The guide is explicit: the HTTP status and the body's business code are two separate signals and
must be checked separately. RayRAG was wrong in both directions — api_error set the body code to
the HTTP status (so the documented 101/102/108/109 never appeared), while some newer endpoints
answered HTTP 200 with code 102 (so a client reading only the status saw success).

New constructors now pair the documented status with the documented code, and the guide's table lives
in code as crate::server::code:

business code	meaning	HTTP
101	invalid argument	400
102	invalid or missing data (includes "you don't own …")	400
103	operation error	400
105	connection error	502
106	still running	400
108	no permission	403
109	unauthenticated	401
409	conflict	409

Measured live:

GET /datasets/{id}/artifacts/nonsense  ->  HTTP 400
                                           {"code":102,"message":"Unknown artifact page type
                                            'nonsense'. Supported: structure, graph, …"}
container panics                       ->  0

The artifact and navigation paths are migrated; the older endpoints still use api_error, and the
internal registry says so explicitly — unmigrated is recorded as unmigrated.

2157 tests pass, 0 failures, including a new regression that asserts every constructor returns the
documented pair and never an empty explanation.