audit(0073): cycle close — lift tier-2 geometry to ledger, finish VETTED_SYMBOLS, drop ephemera

Cycle-close audit: drift-clean on all load-bearing invariants (C7/C8/C15 hold; geometry stays non-scalar metadata, the Source seam still carries only (Timestamp, Scalar); scope boundary held — no resolver, quote_currency still &'static str, both #124's).

Tidy: completed the VETTED_SYMBOLS consolidation the feat commit over-claimed — migrated the two remaining inline vetted-symbol arrays in the crate-internal unit tests (instrument_spec_pip_value_matches_contract_times_pip, instrument_spec_ids_are_distinct) to the const, so #140 now extends one list.

Ledger: lifted this cycle's durable rationale into the C15 realization note (docs/design/INDEX.md) — the floor now carries tick_size/digits, and the recorded-metadata tier-2 source (instrument_geometry over symbol_meta -> neutral InstrumentGeometry, cross-checked against the authored floor) now exists at the ingestion edge; the tier-composing resolver remains #124.

Drop the ephemeral cycle spec + plan (docs/specs, docs/plans) per the lifecycle convention; durable rationale now in the ledger + the #143 thread.

refs #143

crates/aura-ingest/src/lib.rs

@@ -532,7 +532,7 @@ mod tests {
     fn instrument_spec_pip_value_matches_contract_times_pip() {
         // pip_value_per_lot == contract_size * pip_size for every vetted instrument
         // (cross-field invariant, not the literals' real-world exactness).
-        for sym in ["GER40", "FRA40", "EURUSD", "GBPUSD", "USDCAD"] {
+        for sym in VETTED_SYMBOLS {
             let s = instrument_spec(sym).expect("vetted symbol");
             assert!(
                 (s.pip_value_per_lot - s.contract_size * s.pip_size).abs() < 1e-9,
@@ -546,7 +546,7 @@ mod tests {
 
     #[test]
     fn instrument_spec_ids_are_distinct() {
-        let ids: Vec<i64> = ["GER40", "FRA40", "EURUSD", "GBPUSD", "USDCAD"]
+        let ids: Vec<i64> = VETTED_SYMBOLS
             .iter()
             .map(|s| instrument_spec(s).expect("vetted symbol").instrument_id)
             .collect();