Fix txid wire encoding and add txid repair utility

Client likes, replies, poll options, and poll votes now embed the
referenced txid in little-endian wire order, matching the indexer's
byte reversal. Add a psf-memo-db repair library and CLI that rewrites
byte-reversed references in likes, postParents, pollOptions, and
pollVotes and rebuilds the postLikes and postChildren indexes, leaving
correct and unknown references untouched and staying idempotent.

By coder.

psf-memo-client/test/unit/hex.test.js

@@ -11,7 +11,11 @@
 
 const test = require('node:test')
 const assert = require('node:assert/strict')
-const { hexToBytes, buildTxidTextPayload } = require('../../src/services/hex')
+const { hexToBytes, buildTxidTextPayload, txidToWireBytes } = require('../../src/services/hex')
+
+// A non-palindromic txid so a missing byte reversal is observable.
+const DISPLAY_TXID = '0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef'
+const WIRE_HEX = 'efcdab8967452301efcdab8967452301efcdab8967452301efcdab8967452301'
 
 test('hexToBytes decodes exactly 64 hex characters into 32 bytes', () => {
   const bytes = hexToBytes('ab'.repeat(32))
@@ -61,3 +65,25 @@ test('buildTxidTextPayload prefixes the raw txid bytes', () => {
   assert.equal(buf[0], 0xab)
   assert.equal(buf.slice(32).toString('utf8'), 'hi')
 })
+
+test('txidToWireBytes reverses the display txid into little-endian wire order', () => {
+  const bytes = txidToWireBytes(DISPLAY_TXID)
+
+  assert.ok(bytes instanceof Uint8Array)
+  assert.equal(Buffer.from(bytes).toString('hex'), WIRE_HEX)
+})
+
+test('txidToWireBytes rejects an invalid txid', () => {
+  assert.throws(
+    () => txidToWireBytes('zz'.repeat(32)),
+    /valid hex string/
+  )
+})
+
+test('buildTxidTextPayload embeds the txid in little-endian wire order', () => {
+  const raw = buildTxidTextPayload(DISPLAY_TXID, 'hi')
+  const buf = Buffer.from(raw)
+
+  assert.equal(buf.slice(0, 32).toString('hex'), WIRE_HEX)
+  assert.equal(buf.slice(32).toString('utf8'), 'hi')
+})

psf-memo-client/test/unit/memo-like.test.js

@@ -0,0 +1,62 @@
+/*
+  Unit tests for the Memo like wire encoding.
+
+  A like action embeds the liked post's transaction txid as 32 raw bytes in
+  little-endian wire order: the reverse of the 64-character display txid. The
+  indexer reverses those bytes back into display order, so the client must
+  reverse before embedding.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+const MemoLike = require('../../src/services/memo-like')
+
+const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+const POST_TXID = '0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef'
+const WIRE_HEX = 'efcdab8967452301efcdab8967452301efcdab8967452301efcdab8967452301'
+
+function makeWallet () {
+  return {
+    walletInfo: { cashAddress: MY_ADDRESS },
+    utxos: [{ txid: 'utxo', value: 100000 }],
+    broadcasts: [],
+    async getUtxos () {
+      return this.utxos
+    },
+    async sendOpReturn (msg, prefix, bchOutput = []) {
+      this.broadcasts.push({ msg, prefix, bchOutput })
+      return 'aa'.repeat(32)
+    }
+  }
+}
+
+test('like broadcasts the post txid in little-endian wire order', async () => {
+  const wallet = makeWallet()
+  const memoLike = new MemoLike({ wallet })
+
+  await memoLike.like(POST_TXID)
+
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, MemoLike.MEMO_LIKE_PREFIX)
+  const raw = wallet.broadcasts[0].msg
+  assert.equal(Buffer.from(raw).toString('hex'), WIRE_HEX)
+})
+
+test('like reflects the post txid in display order on the feed store', async () => {
+  const wallet = makeWallet()
+  const added = []
+  const feed = {
+    addLike (like) {
+      added.push(like)
+    },
+    posts: []
+  }
+  const memoLike = new MemoLike({ wallet, feed })
+
+  await memoLike.like(POST_TXID)
+
+  assert.equal(added.length, 1)
+  assert.equal(added[0].postTxid, POST_TXID)
+})

psf-memo-client/test/unit/memo-poll-option.test.js

@@ -13,7 +13,8 @@ const assert = require('node:assert/strict')
 const MemoPollOption = require('../../src/services/memo-poll-option')
 
 const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
-const POLL_TXID = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
+// A non-palindromic txid so a missing byte reversal is observable.
+const POLL_TXID = '0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef'
 
 function makeWallet (address = MY_ADDRESS) {
   return {

psf-memo-client/test/unit/memo-poll-vote.test.js

@@ -13,7 +13,8 @@ const assert = require('node:assert/strict')
 const MemoPollVote = require('../../src/services/memo-poll-vote')
 
 const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
-const POLL_TXID = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
+// A non-palindromic txid so a missing byte reversal is observable.
+const POLL_TXID = '0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef'
 
 function makeWallet (address = MY_ADDRESS) {
   return {

psf-memo-client/test/unit/memo-reply.test.js

@@ -0,0 +1,61 @@
+/*
+  Unit tests for the Memo reply wire encoding.
+
+  A reply action embeds the parent transaction txid as 32 raw bytes in
+  little-endian wire order: the reverse of the 64-character display txid. The
+  indexer reverses those bytes back into display order, so the client must
+  reverse before embedding.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+const MemoReply = require('../../src/services/memo-reply')
+
+const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+const PARENT_TXID = '0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef'
+const WIRE_HEX = 'efcdab8967452301efcdab8967452301efcdab8967452301efcdab8967452301'
+
+function makeWallet () {
+  return {
+    walletInfo: { cashAddress: MY_ADDRESS },
+    broadcasts: [],
+    async getUtxos () {
+      return []
+    },
+    async sendOpReturn (msg, prefix) {
+      this.broadcasts.push({ msg, prefix })
+      return 'aa'.repeat(32)
+    }
+  }
+}
+
+test('reply broadcasts the parent txid in little-endian wire order', async () => {
+  const wallet = makeWallet()
+  const memoReply = new MemoReply({ wallet })
+
+  await memoReply.reply('hello memo', PARENT_TXID)
+
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, MemoReply.MEMO_REPLY_PREFIX)
+  const buf = Buffer.from(wallet.broadcasts[0].msg)
+  assert.equal(buf.slice(0, 32).toString('hex'), WIRE_HEX)
+  assert.equal(buf.slice(32).toString('utf8'), 'hello memo')
+})
+
+test('reply reflects the parent txid in display order on the thread store', async () => {
+  const wallet = makeWallet()
+  const added = []
+  const thread = {
+    addReply (reply) {
+      added.push(reply)
+    }
+  }
+  const memoReply = new MemoReply({ wallet, thread })
+
+  await memoReply.reply('hello memo', PARENT_TXID)
+
+  assert.equal(added.length, 1)
+  assert.equal(added[0].parentTxid, PARENT_TXID)
+})