feat(config): expand pool registry to 76 mainnet pools, add Eden + Rsync builders

WS-1.6 / WS-1.7 partial — implements the config-only half of #71.

Pool registry: 3 → 76 curated high-TVL Ethereum mainnet pools tiered
hot/warm/cold across all 6 supported protocols (UniV2, UniV3, Sushi,
Curve, Balancer V2, Bancor V3). Auto-population to the full 5,000+
target tracked separately in #120 (discovery pipeline + per-builder
Prometheus metrics).

Builders: add Eden + Rsync to builders.yaml using the existing api_key
auth pattern. Default to auth_type "none" so executor startup stays
clean for default deployments — operators flip to api_key + set
EDEN_API_KEY / RSYNC_API_KEY in .env to activate.

Tests: relax engine bootstrap_pools assertion from exact-3 to >=3
(anchor USDC/WETH pools) so the test stays robust as pools.toml grows.
Update internal/config builders test to expect the four configured
builders.

Refs: #71, #120

Author: Pablosinyores

.env.example

@@ -25,6 +25,13 @@ DASHBOARD_PORT=8080
 SEARCHER_KEY=your_searcher_wallet_private_key_here
 # FLASHBOTS_AUTH_KEY=your_flashbots_key
 
+# Block builder API keys (referenced by config/builders.yaml via ${VAR} expansion).
+# Leave unset to disable submission to that builder; the executor will still
+# fan-out to the remaining configured builders.
+# TITAN_API_KEY=
+# EDEN_API_KEY=
+# RSYNC_API_KEY=
+
 # Observability - Alertmanager Slack routing.
 # Create an incoming webhook at https://api.slack.com/messaging/webhooks and paste the full URL here.
 # The Alertmanager container substitutes this value into alertmanager.yml at startup, so the webhook

config/builders.yaml

@@ -10,6 +10,23 @@ builders:
     timeout_ms: 2000
     auth_type: "none"
     # To use API key auth, set auth_type: "api_key" and auth_key: "${TITAN_API_KEY}"
+  - name: "eden"
+    url: "https://api.edennetwork.io/v1/bundle"
+    enabled: true
+    timeout_ms: 2000
+    auth_type: "none"
+    # Eden requires an API key for production. Set auth_type: "api_key" and
+    # auth_key: "${EDEN_API_KEY}" once the env var is provisioned in .env.
+    # Validation rejects api_key entries with empty keys, so this defaults to
+    # "none" to keep startup clean — submissions without auth will be rejected
+    # by the relay until the key is wired.
+  - name: "rsync"
+    url: "https://rsync-builder.xyz"
+    enabled: true
+    timeout_ms: 2000
+    auth_type: "none"
+    # Same opt-in pattern as Eden. Set auth_type: "api_key" and
+    # auth_key: "${RSYNC_API_KEY}" once the env var is provisioned in .env.
 
 submission:
   fan_out: true