chore(fast-inbox): drop inHash from the L1 checkpoint header and delete FrontierLib (A-1387)

Remove inHash from the ProposedHeader struct and its hash preimage in
ProposedHeaderLib, keeping the packing byte-for-byte in lockstep with the noir
and stdlib checkpoint headers. Update the decoder base struct and the propose
test helpers, and regenerate the checkpoint fixtures (drop header.inHash,
recompute headerHash).

Delete FrontierLib and its only remaining users: the parity cross-check test
(Parity.t.sol, which verified the deleted parity circuits) and the frontier
merkle test/harness. The frontier tree is gone from both circuits and L1.

Author: spalladino

l1-contracts/src/core/libraries/crypto/FrontierLib.sol

@@ -21,7 +21,6 @@ struct ProposedHeader {
   bytes32 lastArchiveRoot;
   bytes32 blockHeadersHash;
   bytes32 blobsHash;
-  bytes32 inHash;
   bytes32 inboxRollingHash;
   bytes32 outHash;
   Slot slotNumber;
@@ -56,7 +55,6 @@ library ProposedHeaderLib {
         _header.lastArchiveRoot,
         _header.blockHeadersHash,
         _header.blobsHash,
-        _header.inHash,
         _header.inboxRollingHash,
         _header.outHash,
         _header.slotNumber,

l1-contracts/src/core/libraries/rollup/ProposedHeaderLib.sol

@@ -164,8 +164,6 @@ contract RollupFieldRangeTest is RollupBase {
     vm.warp(max(block.timestamp, Timestamp.unwrap(ts)));
 
     _populateInbox(full.populate.sender, full.populate.recipient, full.populate.l1ToL2Content);
-    // The header's inHash field is an unconstrained pass-through hint post-flip; propose does not check it.
-    header.inHash = bytes32(0);
     header.gasFees.feePerL2Gas = SafeCast.toUint128(rollup.getManaMinFeeAt(ts, true));
 
     // Every field the range check guards, set to the maximal in-range value.

l1-contracts/test/Parity.t.sol

@@ -46,7 +46,6 @@ contract DecoderBase is TestBase {
     address coinbase;
     bytes32 feeRecipient;
     GasFees gasFees;
-    bytes32 inHash;
     bytes32 inboxRollingHash;
     bytes32 lastArchiveRoot;
     bytes32 outHash;
@@ -104,7 +103,6 @@ contract DecoderBase is TestBase {
           lastArchiveRoot: full.checkpoint.header.lastArchiveRoot,
           blockHeadersHash: full.checkpoint.header.blockHeadersHash,
           blobsHash: full.checkpoint.header.blobsHash,
-          inHash: full.checkpoint.header.inHash,
           inboxRollingHash: full.checkpoint.header.inboxRollingHash,
           outHash: full.checkpoint.header.outHash,
           slotNumber: Slot.wrap(full.checkpoint.header.slotNumber),

l1-contracts/test/RollupFieldRange.t.sol

@@ -169,8 +169,6 @@ contract RollupBase is DecoderBase {
     vm.warp(max(block.timestamp, Timestamp.unwrap(full.checkpoint.header.timestamp)));
 
     _populateInbox(full.populate.sender, full.populate.recipient, full.populate.l1ToL2Content);
-    // The header's inHash field is an unconstrained pass-through hint post-flip; propose does not check it.
-    full.checkpoint.header.inHash = bytes32(0);
     // Streaming Inbox (AZIP-22 Fast Inbox): reference the newest bucket so the checkpoint consumes all messages
     // seeded above and the mandatory-consumption assert is trivially satisfied (a wrong ref could only revert).
     uint256 bucketHint = rollup.getInbox().getCurrentBucketSeq();

l1-contracts/test/base/DecoderBase.sol

@@ -130,18 +130,17 @@ abstract contract EscapeHatchIntegrationBase is ValidatorSelectionTestBase {
    * @dev Uses:
    *   - archive: GENESIS_ARCHIVE_ROOT
    *   - oracleInput: zero
-   *   - header fields from fixture for blockHeadersHash/blobsHash/inHash/outHash, rest overridden
+   *   - header fields from fixture for blockHeadersHash/blobsHash/outHash, rest overridden
    */
   function _buildProposeArgs(address _proposer) internal view returns (ProposeArgs memory args, bytes memory blobs) {
     bytes32 archive = bytes32(Constants.GENESIS_ARCHIVE_ROOT);
     Slot slotNumber = rollup.getCurrentSlot();
 
-    // Build header fresh, only copying blockHeadersHash/blobsHash/inHash/outHash from fixture
+    // Build header fresh, only copying blockHeadersHash/blobsHash/outHash from fixture
     ProposedHeader memory header = ProposedHeader({
       lastArchiveRoot: archive,
       blockHeadersHash: full.checkpoint.header.blockHeadersHash,
       blobsHash: full.checkpoint.header.blobsHash,
-      inHash: full.checkpoint.header.inHash,
       inboxRollingHash: full.checkpoint.header.inboxRollingHash,
       outHash: full.checkpoint.header.outHash,
       slotNumber: slotNumber,

l1-contracts/test/base/RollupBase.sol

@@ -34,7 +34,6 @@
       "lastArchiveRoot": "0x177a4955b31ecaafad999753938a44e526b54c5ba5d536688227f85f15cfbdf5",
       "blockHeadersHash": "0x2e3e0911389bc48fa8126a93273d016cc7dc08019f8ffc5f1f5ae7d90745eaa2",
       "blobsHash": "0x00e5b752fe6bc2154155ff3a979c4c5fa91d3ac0d716169ac521e1560fd83b2b",
-      "inHash": "0x00de7b349d2306334734e4f58b1302a6ed5a6c796a706f6597a5641b6d468223",
       "inboxRollingHash": "0x00cad6497cf81748167158f149ba70c31f34c68b0ae1b156117de63e073d14b5",
       "outHash": "0x00c95e0ceb41951039e1592745ec2faea9866f6eaf01bf189a4463b4143af093",
       "slotNumber": 99,
@@ -48,7 +47,7 @@
       "totalManaUsed": 0,
       "accumulatedFees": 0
     },
-    "headerHash": "0x0002fc455005d993521be4e6f8ed92d1e0b50e58b21445881c87d02ed51a1e4c",
+    "headerHash": "0x00230a553b85ec7931eded45ec1ea096e47789226758b16dca0403f5ab53f3d6",
     "numTxs": 0
   }
 }

l1-contracts/test/escape-hatch/integration/EscapeHatchIntegrationBase.sol

@@ -34,7 +34,6 @@
       "lastArchiveRoot": "0x09d45c1e01b8596153838a068ddb470ead95e6e1e151f40b4d48664c1e311af6",
       "blockHeadersHash": "0x0b3bda1754ca30707b8c0bbe72760c68e574cf23309e7e4fd7cabea36b4078da",
       "blobsHash": "0x000e9acabf609c9c113078ecb383ba6310573ce246958b605452132617d2c960",
-      "inHash": "0x006504de282a40084bb8098456a915c645d53482d351db52fa9433b6cd638763",
       "inboxRollingHash": "0x0080dbf2bd9576e81fd99fc0f9d35bfd7fc15a6221d0b6e1e92a1884f14d0c84",
       "outHash": "0x00c95e0ceb41951039e1592745ec2faea9866f6eaf01bf189a4463b4143af093",
       "slotNumber": 102,
@@ -48,7 +47,7 @@
       "totalManaUsed": 0,
       "accumulatedFees": 0
     },
-    "headerHash": "0x00120ecaf7a72f61adf3c8ee180acd930401221668a4792a8f91584755840d16",
+    "headerHash": "0x00a184a160ada9af4ba75961ba596043d76f56c75b2e7e9652a0c162a7bf59b9",
     "numTxs": 0
   }
 }

l1-contracts/test/fixtures/empty_checkpoint_1.json

@@ -67,7 +67,6 @@
       "lastArchiveRoot": "0x177a4955b31ecaafad999753938a44e526b54c5ba5d536688227f85f15cfbdf5",
       "blockHeadersHash": "0x087b6f59388fa4207876ee1b50521ff838d6eed422d0ad07ff996393f32a77e6",
       "blobsHash": "0x001bef3ff3f657c565ff86d5072186f7f2bfddb8a31ca0714562c164fe954d84",
-      "inHash": "0x00de7b349d2306334734e4f58b1302a6ed5a6c796a706f6597a5641b6d468223",
       "inboxRollingHash": "0x00cad6497cf81748167158f149ba70c31f34c68b0ae1b156117de63e073d14b5",
       "outHash": "0x00cffdbb0e7f5e164d314d781d38ae31230910a3bae4c34e7df6222df71b1539",
       "slotNumber": 99,
@@ -81,7 +80,7 @@
       "totalManaUsed": 0,
       "accumulatedFees": 0
     },
-    "headerHash": "0x00c1431d117825d25f8169e35eb70ed4b16c0fc4b3cac85506852c240d03740e",
+    "headerHash": "0x00f1c11fddfca8ff6073d1715c8b886d501facad96b7b032fb440462849697b8",
     "numTxs": 4
   }
 }