railway: pin start command to host/start.sh (config-as-code)

The copybot service's custom start command was 'bash start.sh' — a relic
of the scratchpad folder it was first deployed from; builds from the repo
root have no root start.sh, so image rebuilds crashed and Railway kept
serving the years-old image (which is also why start.sh changes never
took effect via redeploy). railway.json now pins the start command;
nixpacks.toml's default no longer points at the retired webhook_receiver.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

nixpacks.toml

@@ -1,11 +1,10 @@
 # Explicit build config for Railway/Nixpacks (pure-stdlib Python service).
-# Default start = the Discord webhook receiver. For the 24/7 copybot worker,
-# deploy a second service from this repo and override the start command with
-#   bash host/start.sh
-# (see host/start.sh for the full setup). git is needed at runtime — the bot
-# persists its book by committing state + feed back to GitHub.
+# Start = the 24/7 copybot worker (bash host/start.sh, also pinned by
+# railway.json's deploy.startCommand). git is needed at runtime — the bot
+# persists its book by committing state + feed back to GitHub. The old
+# webhook_receiver default is retired (archive/webhook_receiver.py).
 [phases.setup]
 nixPkgs = ["python311", "git"]
 
 [start]
-cmd = "python3 webhook_receiver.py"
+cmd = "bash host/start.sh"

railway.json

@@ -0,0 +1,8 @@
+{
+  "$schema": "https://railway.com/railway.schema.json",
+  "deploy": {
+    "startCommand": "bash host/start.sh",
+    "restartPolicyType": "ON_FAILURE",
+    "restartPolicyMaxRetries": 10
+  }
+}