feat: add com.atproto.sync.getRecord endpoint

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

src/pds.js

···
   '/xrpc/com.atproto.sync.getRepo': {
     handler: (pds, req, url) => pds.handleGetRepo()
   },
+  '/xrpc/com.atproto.sync.getRecord': {
+    handler: (pds, req, url) => pds.handleSyncGetRecord(url)
+  },
   '/xrpc/com.atproto.sync.subscribeRepos': {
     handler: (pds, req, url) => pds.handleSubscribeRepos(req, url)
   }
···
       data: new Uint8Array(b.data)
     }))
     const car = buildCarFile(commits[0].cid, blocksForCar)
+    return new Response(car, {
+      headers: { 'content-type': 'application/vnd.ipld.car' }
+    })
+  }
+
+  async handleSyncGetRecord(url) {
+    const collection = url.searchParams.get('collection')
+    const rkey = url.searchParams.get('rkey')
+    if (!collection || !rkey) {
+      return Response.json({ error: 'InvalidRequest', message: 'missing collection or rkey' }, { status: 400 })
+    }
+    const did = await this.getDid()
+    const uri = `at://${did}/${collection}/${rkey}`
+    const rows = this.sql.exec(
+      `SELECT cid FROM records WHERE uri = ?`, uri
+    ).toArray()
+    if (rows.length === 0) {
+      return Response.json({ error: 'RecordNotFound', message: 'record not found' }, { status: 404 })
+    }
+    // Get the record block
+    const recordCid = rows[0].cid
+    const blockRows = this.sql.exec(
+      `SELECT cid, data FROM blocks WHERE cid = ?`, recordCid
+    ).toArray()
+    if (blockRows.length === 0) {
+      return Response.json({ error: 'RecordNotFound', message: 'block not found' }, { status: 404 })
+    }
+    const blocks = blockRows.map(b => ({
+      cid: b.cid,
+      data: new Uint8Array(b.data)
+    }))
+    const car = buildCarFile(recordCid, blocks)
     return new Response(car, {
       headers: { 'content-type': 'application/vnd.ipld.car' }
     })