sbc: document reversed elgReq ordinal finding; elgReq stays empty

Reversed from the pinned CardsDLL (4706a881): eligibilityKey and
eligibilityOperation are localization ordinals (LOC_SBC_ELG_KEY_%d),
not the atom hex ids. The client's only consumer is the requirement-
display string builder at ~0x1800ef900 (formats via indexed locale
keys, no comparison/gate). The ordinal->string map lives only in the
packed locale (absent from all assets we hold), so any emitted value
would render the WRONG requirement text. Submission stays fully
validated server-side by Core; the empty elgReq is display-only.
Correct ENDPOINT_MAP.md's implied atom-id==ordinal assumption and
pin the exact remaining blocker at the emit site.

openfut-adapter-fifa17/src/fut/sbc.rs

@@ -116,6 +116,15 @@ pub fn challenges_body(set_id: i64, challenges: &[ChallengeView]) -> Value {
                 "status": "OPEN",
                 "timesCompleted": times_completed,
                 "awards": [],
+                // `elgReq` stays empty deliberately. Reversed from the pinned CardsDLL
+                // (2026-08-19, see ENDPOINT_MAP.md "Shared record shapes"): the client
+                // consumes `eligibilityKey`/`eligibilityOperation` only as ordinals that
+                // index the packed locale (`LOC_SBC_ELG_KEY_%d`) to render requirement
+                // text — it does NOT validate on them. The ordinal->string map is not
+                // recoverable from any asset we have, so any value we emit would show the
+                // WRONG requirement to the player. Submission is validated server-side by
+                // Core regardless; leaving this empty is display-only, never a correctness
+                // gap. Populate ONLY once the locale ordinal map is captured.
                 "elgReq": []
             })
         })
@@ -360,8 +369,16 @@ mod tests {
         assert_eq!(
             parse_wire_item_ids(retail).unwrap(),
             [
-                100_004_227, 100_004_233, 100_001_317, 100_001_531, 100_000_966,
-                100_001_947, 100_000_169, 100_002_017, 100_002_765, 100_000_147,
+                100_004_227,
+                100_004_233,
+                100_001_317,
+                100_001_531,
+                100_000_966,
+                100_001_947,
+                100_000_169,
+                100_002_017,
+                100_002_765,
+                100_000_147,
                 100_000_311
             ],
             "exactly the 11 non-zero players in wire order; manager and empty slots ignored"