fix: set language singleton early so git diff auto-detection works for all languages

The language singleton was only set after function discovery, but get_git_diff()
needs it during discovery to filter by file extension.

- config_parser.py: set config["language"] based on config file type (codeflash.toml
  → java, pyproject.toml → python) so all project types return a language
- cli.py: call set_current_language() in process_pyproject_config() using the
  config value, before the optimizer runs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mashraf-222

code_to_optimize/java/src/main/java/com/example/Fibonacci.java

@@ -19,7 +19,7 @@ public static long fibonacci(int n) {
             throw new IllegalArgumentException("Fibonacci not defined for negative numbers");
         }
         if (n <= 1) {
-            return n;
+            return n; // base case
         }
         return fibonacci(n - 1) + fibonacci(n - 2);
     }

codeflash/cli_cmds/cli.py

@@ -109,18 +109,13 @@ def process_pyproject_config(args: Namespace) -> Namespace:
     assert args.module_root is not None, "--module-root must be specified"
     assert Path(args.module_root).is_dir(), f"--module-root {args.module_root} must be a valid directory"
 
-    # Determine project language from explicit config or config file name.
-    # Java projects use codeflash.toml but don't always have an explicit language field.
-    config_language = pyproject_config.get("language")
-    if config_language is None and pyproject_file_path.name == "codeflash.toml":
-        config_language = "java"
-    is_js_ts_project = config_language in ("javascript", "typescript")
-    is_java_project = config_language == "java"
+    is_js_ts_project = pyproject_config.get("language") in ("javascript", "typescript")
+    is_java_project = pyproject_config.get("language") == "java"
 
     # Set the language singleton early so downstream code (e.g. get_git_diff)
     # can use current_language_support() before function discovery.
-    if config_language:
-        set_current_language(config_language)
+    if pyproject_config.get("language"):
+        set_current_language(pyproject_config["language"])
 
     # Set the test framework singleton for JS/TS projects
     if is_js_ts_project and pyproject_config.get("test_framework"):

codeflash/code_utils/config_parser.py

@@ -160,7 +160,11 @@ def parse_config_file(
     if config == {} and lsp_mode:
         return {}, config_file_path
 
-    # Preserve language field if present (important for Java/JS projects using codeflash.toml)
+    # Set language based on config file type if not already present.
+    # JS/TS projects set this in parse_package_json_config; for toml projects we infer it here.
+    if "language" not in config:
+        config["language"] = "java" if config_file_path.name == "codeflash.toml" else "python"
+
     # default values:
     path_keys = ["module-root", "tests-root", "benchmarks-root"]
     path_list_keys = ["ignore-paths"]