aider: Added max_chat_history_tokens as an explicit argument to the Coder.__init__ method and passed args.max_chat_history_tokens when creating the Coder instance in main().

# Aider chat conversation:

USER: don't use kwargs, add it as an explicit arg

ASSISTANT: Here is the *SEARCH/REPLACE block* to add `max_chat_history_tokens` as an explicit argument instead of using `**kwargs`:

aider/coders/base_coder.py
```python
<<<<<<< SEARCH
    def __init__(
        self,
        main_model,
        io,
        fnames=None,
        git_dname=None,
        pretty=True,
        show_diffs=False,
        auto_commits=True,
        dirty_commits=True,
        dry_run=False,
        map_tokens=1024,
        verbose=False,
        assistant_output_color="blue",
        code_theme="default",
        stream=True,
        use_git=True,
        voice_language=None,
        aider_ignore_file=None,
        cur_messages=None,
        done_messages=None,
    ):
=======
    def __init__(
        self,
        main_model,
        io,
        fnames=None,
        git_dname=None,
        pretty=True,
        show_diffs=False,
        auto_commits=True,
        dirty_commits=True,
        dry_run=False,
        map_tokens=1024,
        verbose=False,
        assistant_output_color="blue",
        code_theme="default",
        stream=True,
        use_git=True,
        voice_language=None,
        aider_ignore_file=None,
        cur_messages=None,
        done_messages=None,
        max_chat_history_tokens=None,
    ):
>>>>>>> REPLACE
```

aider/main.py
```python
<<<<<<< SEARCH
        coder = Coder.create(
            main_model=main_model,
            edit_format=args.edit_format,
            io=io,
            ##
            fnames=fnames,
            git_dname=git_dname,
            pretty=args.pretty,
            show_diffs=args.show_diffs,
            auto_commits=args.auto_commits,
            dirty_commits=args.dirty_commits,
            dry_run=args.dry_run,
            map_tokens=args.map_tokens,
            verbose=args.verbose,
            assistant_output_color=args.assistant_output_color,
            code_theme=args.code_theme,
            stream=args.stream,
            use_git=args.git,
            voice_language=args.voice_language,
            aider_ignore_file=args.aiderignore,
        )
=======
        coder = Coder.create(
            main_model=main_model,
            edit_format=args.edit_format,
            io=io,
            ##
            fnames=fnames,
            git_dname=git_dname,
            pretty=args.pretty,
            show_diffs=args.show_diffs,
            auto_commits=args.auto_commits,
            dirty_commits=args.dirty_commits,
            dry_run=args.dry_run,
            map_tokens=args.map_tokens,
            verbose=args.verbose,
            assistant_output_color=args.assistant_output_color,
            code_theme=args.code_theme,
            stream=args.stream,
            use_git=args.git,
            voice_language=args.voice_language,
            aider_ignore_file=args.aiderignore,
            max_chat_history_tokens=args.max_chat_history_tokens,
        )
>>>>>>> REPLACE
```

This adds `max_chat_history_tokens` as an explicit argument to the `Coder.__init__` method, and passes `args.max_chat_history_tokens` when creating the `Coder` instance in `main()`.

aider/coders/base_coder.py

@@ -193,6 +193,7 @@ class Coder:
         aider_ignore_file=None,
         cur_messages=None,
         done_messages=None,
+        max_chat_history_tokens=None,
     ):
         if not fnames:
             fnames = []