allow multiple tool calls, log warnings if there are duplicate calls.

controlled via a flag to the agent config:
allow_multiple_tool_calls = true

crates/g3-config/src/lib.rs

@@ -70,6 +70,7 @@ pub struct AgentConfig {
     pub max_context_length: Option<u32>,
     pub fallback_default_max_tokens: usize,
     pub enable_streaming: bool,
+    pub allow_multiple_tool_calls: bool,
     pub timeout_seconds: u64,
     pub auto_compact: bool,
     pub max_retry_attempts: u32,
@@ -145,6 +146,7 @@ impl Default for Config {
                 max_context_length: None,
                 fallback_default_max_tokens: 8192,
                 enable_streaming: true,
+                allow_multiple_tool_calls: false,
                 timeout_seconds: 60,
                 auto_compact: true,
                 max_retry_attempts: 3,
@@ -265,6 +267,7 @@ impl Config {
                 max_context_length: None,
                 fallback_default_max_tokens: 8192,
                 enable_streaming: true,
+                allow_multiple_tool_calls: false,
                 timeout_seconds: 60,
                 auto_compact: true,
                 max_retry_attempts: 3,