Merge main: relay hotfixes and the docs pages

Conflicts were comment wording only, from the WordPress purge. Kept this
branch's prose: main's side carries the rename's artifacts ('the the
previous platform'), and the code either side registers is identical.
Verified after resolving — one api index, no wp-json index, the
federation refusal path, HomeRelays, and FN_ACCOUNTS_URL all present.

engine/src/test/kotlin/io/flamenet/e2e/PublishedVectorsTest.kt

@@ -84,6 +84,29 @@ class PublishedVectorsTest {
         assertEquals(12, formatted.split(" ").size)
     }
 
+    @Test
+    fun `account identity encodes exactly as published`() {
+        val ai = vectors.getJSONObject("accountIdentity")
+        val key = java.util.Base64.getDecoder().decode(ai.getString("accountKeyB64"))
+
+        assertEquals(ai.getString("encoded"), FNID.encode(key))
+        assertEquals(ai.getString("address"), FNID.address(key))
+
+        val claim = ai.getJSONObject("claim")
+        val input = claim.getJSONObject("input")
+        assertEquals(
+            claim.getString("canonical"),
+            String(
+                FNID.claimCanonical(
+                    audience = input.getString("audience"),
+                    userId = input.getLong("userId"),
+                    accountKeyB64 = input.getString("accountKeyB64"),
+                ),
+                Charsets.UTF_8,
+            ),
+        )
+    }
+
     @Test
     fun `canonical leaf encodes and hashes exactly as published`() {
         val leaf = vectors.getJSONObject("keyLog").getJSONObject("canonicalLeaf")