Fix issue with fallbacks and the initial client (#1089)

<!-- ELLIPSIS_HIDDEN -->



> [!IMPORTANT]
> Added retry policies to `CustomGPT4oMini` and `CustomHaiku`, corrected
strategies for round-robin and fallback clients in `clients.baml`.
> 
>   - **Retry Policies**:
>     - Added `retry_policy Exponential` to `CustomGPT4oMini`.
>     - Added `retry_policy Constant` to `CustomHaiku`.
>   - **Strategies**:
> - Corrected round-robin strategy in `CustomFast` to use
`CustomGPT4oMini` and `CustomHaiku`.
> - Corrected fallback strategy in `OpenaiFallback` to use
`CustomGPT4oMini` twice.
>   - **Retry Policy Definitions**:
> - Defined `retry_policy Constant` with `max_retries 3`, `delay_ms
200`.
> - Defined `retry_policy Exponential` with `max_retries 2`, `delay_ms
300`, `multiplier 1.5`, `max_delay_ms 10000`.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 8b092f3. It will automatically
update as commits are pushed.</sup>

<!-- ELLIPSIS_HIDDEN -->

engine/baml-runtime/src/cli/initial_project/baml_src/clients.baml

@@ -10,6 +10,7 @@ client<llm> CustomGPT4o {
 
 client<llm> CustomGPT4oMini {
   provider openai
+  retry_policy Exponential
   options {
     model "gpt-4o-mini"
     api_key env.OPENAI_API_KEY
@@ -27,24 +28,48 @@ client<llm> CustomSonnet {
 
 client<llm> CustomHaiku {
   provider anthropic
+  retry_policy Constant
   options {
     model "claude-3-haiku-20240307"
     api_key env.ANTHROPIC_API_KEY
   }
 }
 
+// https://docs.boundaryml.com/docs/snippets/clients/round-robin
 client<llm> CustomFast {
   provider round-robin
   options {
     // This will alternate between the two clients
-    strategy [GPT4oMini, Haiku]
+    strategy [CustomGPT4oMini, CustomHaiku]
   }
 }
 
+// https://docs.boundaryml.com/docs/snippets/clients/fallback
 client<llm> OpenaiFallback {
   provider fallback
   options {
     // This will try the clients in order until one succeeds
-    strategy [GPT4o, GPT4oMini]
+    strategy [CustomGPT4oMini, CustomGPT4oMini]
+  }
+}
+
+// https://docs.boundaryml.com/docs/snippets/clients/retry
+retry_policy Constant {
+  max_retries 3
+  // Strategy is optional
+  strategy {
+    type constant_delay
+    delay_ms 200
+  }
+}
+
+retry_policy Exponential {
+  max_retries 2
+  // Strategy is optional
+  strategy {
+    type exponential_backoff
+    delay_ms 300
+    mutliplier 1.5
+    max_delay_ms 10000
   }
 }