/query does not forward RERUM's Pagination-* response headers #131

Summary

RERUM API PR rerum_server_nodejs#310, deployed on devstore now, reports pagination on /query responses with four headers:

Pagination-Limit: 500
Pagination-Skip: 0
Pagination-Limit-Max: 500
Pagination-Skip-Max: 100000

The applied values come back on every paged 200.
The two maximums also come back on a limit/skip rejection, such as a skip past the maximum.

TinyNode's routes/query.js does not forward them.
It reads only the body from RERUM (routes/query.js#L37-L49) and builds a fresh response, so the headers are dropped on both the success and the error path.

Why this matters

A TinyNode client cannot tell a truncated page from a final one.
?limit=1000 is clamped to 500 by RERUM, and devstore says so in Pagination-Limit: 500.
tinydev returns the same 500 records with nothing on the wire to say they were clamped.

On an error, a client that hits the skip ceiling cannot read Pagination-Skip-Max to learn where the ceiling is.
The 502 status is fine; the headers just need to come along with it.

Evidence

Verified 2026-09-14, read-only, body {"type":"Annotation"}.

tinydev already sends Access-Control-Expose-Headers: *, so browser clients can read the headers once they are forwarded.

Proposed change

Copy any Pagination-* headers RERUM returned onto TinyNode's response, before branching on resp.ok, so they survive both the 200 and the 502.

const PAGINATION_HEADERS = ["Pagination-Limit", "Pagination-Skip", "Pagination-Limit-Max", "Pagination-Skip-Max"]

const rerumResponse = await fetchRerum(queryURL, queryOptions)
.then(async (resp) => {
  for (const header of PAGINATION_HEADERS) {
    const value = resp.headers.get(header)
    if (value !== null) res.set(header, value)
  }
  if (resp.ok) return resp.json()
  // ...existing error handling, unchanged
})

Headers set on res before the throw are kept when the route's catch sends the 502.
When RERUM sends none, for example store.rerum.io before #310 is released, nothing is forwarded.

The fetch mocks in test/routes/query.test.js return objects with no headers, so they need headers: new Headers() once the route reads them.

Acceptance criteria

• A successful /query response carries every Pagination-* header RERUM returned
• A 502 from /query carries every Pagination-* header RERUM returned on its error response
• No Pagination-* headers are added when RERUM does not send them
• Tests cover forwarding on both the success and error paths