f - Scan full history in is_outpoint_spent

PR #4565 moved chanmon_consistency_target to the real-hashes runner, so
txids no longer collide across unrelated outpoints. The 6-block window
added to dodge those collisions is no longer needed; scanning the full
block history is correct and matches the behavior before the fake-hashes
workaround.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jkczyz

fuzz/src/chanmon_consistency.rs

@@ -207,11 +207,7 @@ impl ChainState {
 	}
 
 	fn is_outpoint_spent(&self, outpoint: &bitcoin::OutPoint) -> bool {
-		// Only check the last 6 blocks (1 confirmation block + 5 post-confirmation) to avoid
-		// false positives from hash collisions in older blocks. Under fuzz hashing, txids have
-		// only 8 effective bits, so unrelated outpoints in old blocks frequently collide.
-		let start = self.blocks.len().saturating_sub(6);
-		self.blocks[start..].iter().any(|(_, txs)| {
+		self.blocks.iter().any(|(_, txs)| {
 			txs.iter().any(|tx| {
 				tx.input.iter().any(|input| input.previous_output == *outpoint)
 			})