node: Fix weight documentation and remove dead firehose weight

- Document that weight 0.0 is intentional (disables from weighted
  selection while keeping the provider for error-retesting)
- Fix contradictory example in full_config.toml that showed weights >1.0
  despite validation rejecting them
- Remove weight from firehose provider config since it is only used
  for RPC providers

Author: DaMandal0rian

node/resources/tests/full_config.toml

@@ -49,15 +49,15 @@ ingestor = "index_0"
 # - Weights must be between 0.0 and 1.0 (inclusive)
 # - Weights are relative - they don't need to sum to 1.0
 # - Traffic is distributed proportionally based on weights
-# - Example: weights [0.2, 0.8] = 20% and 80% traffic distribution
-# - Example: weights [1.0, 2.0, 1.0] = 25%, 50%, 25% distribution
+# - Example: weights [0.3, 0.5, 0.2] = 30%, 50%, 20% traffic distribution
 # - At least one provider must have weight > 0.0
+# - Weight is only used for RPC providers; it is ignored for firehose providers
 [chains.mainnet]
 shard = "primary"
 provider = [
   { label = "mainnet-0", url = "http://rpc.mainnet.io", features = ["archive", "traces"], weight = 0.1 },
   { label = "mainnet-1", details = { type = "web3call", url = "http://rpc.mainnet.io", features = ["archive", "traces"] }, weight = 0.2 },
-  { label = "firehose", details = { type = "firehose", url = "http://localhost:9000", features = [] }, weight = 0.3 },
+  { label = "firehose", details = { type = "firehose", url = "http://localhost:9000", features = [] } },
 ]
 
 [chains.ropsten]

node/src/config.rs

@@ -732,6 +732,8 @@ const DEFAULT_PROVIDER_FEATURES: [&str; 2] = ["traces", "archive"];
 impl Provider {
     fn validate(&mut self) -> Result<()> {
         validate_name(&self.label).context("illegal provider name")?;
+        // Weight of 0.0 is intentional: it disables the provider from weighted selection
+        // while keeping it available for error-retesting and non-weighted fallback paths.
         if self.weight < 0.0 || self.weight > 1.0 {
             bail!("provider {} must have a weight between 0 and 1", self.label);
         }