feat(attribution): carry a miner's name across chains by reward preimage

Live telemetry names the miners who win often and leaves everyone else as a
hex string. Measured on mainnet: of 22 miners, 2 were named and 14 had no name
available anywhere — but 6 already had one on Planck, under the same reward
preimage. Those 6 are exactly the small operators the naming is worst for,
because a name needs a block whose first reporter the feed could separate and
they win few blocks.

The preimage is derived from a secret only its owner holds, so the same
preimage on two chains is the same operator. That is an inference the site can
stand behind, unlike guessing from timing — and it is the only lever that works
without waiting on the feed at all.

It is a separate `AttributionSource` and renders as one. `Carried` names carry
no confidence and no votes, because they assert nothing about this chain: only
that this is who the operator was last known to be. Any live attribution here
outranks one, and the row shows an `elsewhere` chip rather than the telemetry
`node` chip so the two can never be read as the same claim.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Jp6a8EDar9ueEhAxzep4V5

.sqlx/query-56b27b0c55bcca16be18d3222c19691fd491bcda14f98fbd1c71e20cbe97d0bf.json

@@ -0,0 +1,28 @@
+{
+  "db_name": "PostgreSQL",
+  "query": "\n            select distinct on (a.miner) a.miner, a.node_name as \"node_name!\"\n            from miner_attribution a\n            where a.chain <> $1\n              and a.node_name is not null\n              and not exists (\n                  select 1 from miner_attribution mine\n                  where mine.chain = $1 and mine.miner = a.miner\n              )\n            order by a.miner, a.updated_at desc\n            ",
+  "describe": {
+    "columns": [
+      {
+        "ordinal": 0,
+        "name": "miner",
+        "type_info": "Text"
+      },
+      {
+        "ordinal": 1,
+        "name": "node_name!",
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Left": [
+        "Text"
+      ]
+    },
+    "nullable": [
+      false,
+      true
+    ]
+  },
+  "hash": "56b27b0c55bcca16be18d3222c19691fd491bcda14f98fbd1c71e20cbe97d0bf"
+}