postprocess: switch from gemini-3-pro-preview to gemini-3-flash-preview for the default

`flash` is cheaper and faster and seems to still be sufficiently capable.

I did have to adjust the prompt slightly to explicitly say to include
the surrounding Rust Markdown code block.
This isn't actually used right now, but is in #1534, so it seems worth preserving.

Author: kkysen

c2rust-postprocess/postprocess/__init__.py

@@ -52,7 +52,7 @@ def build_arg_parser() -> argparse.ArgumentParser:
         "--model-id",
         type=str,
         required=False,
-        default="gemini-3-pro-preview",
+        default="gemini-3-flash-preview",
         help="ID of the LLM model to use (default: gemini-3-pro-preview)",
     )
 

c2rust-postprocess/postprocess/transforms.py

@@ -107,7 +107,8 @@ def transfer_comments(
             Transfer the comments from the following C function to the corresponding Rust function.
             Do not add any comments that are not present in the C function.
             Use Rust doc comment syntax (///) where appropriate (e.g., for function documentation).
-            Respond with the Rust function definition with the transferred comments; say nothing else.
+            Respond with the Rust function definition with the transferred comments
+            in a Rust Markdown code block; say nothing else.
             """  # noqa: E501
             prompt_text = dedent(prompt_text).strip()
 

…f5dc232f35146250b6d2d1fb29/metadata.toml …b1004cc8b0a527e70b4982ea59/metadata.tomlc2rust-postprocess/tests/llm-cache/CommentTransfer/partition/bf27c23abbb2f5c2d7dba1891b748252983959f5dc232f35146250b6d2d1fb29/metadata.toml renamed to c2rust-postprocess/tests/llm-cache/CommentTransfer/partition/9c5f0dcfa75e9295565171e257b58573c8967fb1004cc8b0a527e70b4982ea59/metadata.toml c2rust-postprocess/tests/llm-cache/CommentTransfer/partition/bf27c23abbb2f5c2d7dba1891b748252983959f5dc232f35146250b6d2d1fb29/metadata.toml renamed to c2rust-postprocess/tests/llm-cache/CommentTransfer/partition/9c5f0dcfa75e9295565171e257b58573c8967fb1004cc8b0a527e70b4982ea59/metadata.toml

@@ -1,6 +1,6 @@
 transform = "CommentTransfer"
 identifier = "partition"
-model = "gemini-3-pro-preview"
+model = "gemini-3-flash-preview"
 response = """```rust
 /// Lomuto Partition Scheme:
 /// Partitions the array so that elements < pivot are on the left, 
@@ -40,7 +40,8 @@ role = "user"
 content = """Transfer the comments from the following C function to the corresponding Rust function.
 Do not add any comments that are not present in the C function.
 Use Rust doc comment syntax (///) where appropriate (e.g., for function documentation).
-Respond with the Rust function definition with the transferred comments; say nothing else.
+Respond with the Rust function definition with the transferred comments
+in a Rust Markdown code block; say nothing else.
 
 C function:
 ```c

…9f5dc232f35146250b6d2d1fb29/response.txt …fb1004cc8b0a527e70b4982ea59/response.txtc2rust-postprocess/tests/llm-cache/CommentTransfer/partition/bf27c23abbb2f5c2d7dba1891b748252983959f5dc232f35146250b6d2d1fb29/response.txt renamed to c2rust-postprocess/tests/llm-cache/CommentTransfer/partition/9c5f0dcfa75e9295565171e257b58573c8967fb1004cc8b0a527e70b4982ea59/response.txt c2rust-postprocess/tests/llm-cache/CommentTransfer/partition/bf27c23abbb2f5c2d7dba1891b748252983959f5dc232f35146250b6d2d1fb29/response.txt renamed to c2rust-postprocess/tests/llm-cache/CommentTransfer/partition/9c5f0dcfa75e9295565171e257b58573c8967fb1004cc8b0a527e70b4982ea59/response.txt

@@ -1,6 +1,6 @@
 transform = "CommentTransfer"
 identifier = "quickSort"
-model = "gemini-3-pro-preview"
+model = "gemini-3-flash-preview"
 response = """```rust
 #[no_mangle]
 pub unsafe extern "C" fn quickSort(
@@ -24,7 +24,8 @@ role = "user"
 content = """Transfer the comments from the following C function to the corresponding Rust function.
 Do not add any comments that are not present in the C function.
 Use Rust doc comment syntax (///) where appropriate (e.g., for function documentation).
-Respond with the Rust function definition with the transferred comments; say nothing else.
+Respond with the Rust function definition with the transferred comments
+in a Rust Markdown code block; say nothing else.
 
 C function:
 ```c