feat: add working directory control for Claude terminal

[ThomasK33]

Working Directory Control for Claude Terminal

This PR adds the ability to fix Claude terminal's working directory regardless of autochdir and buffer-local cwd changes. The feature provides three options (in precedence order):

1. cwd_provider(ctx): A function that returns a directory string, receiving context with { file, file_dir, cwd }
2. cwd: A static path to use as working directory
3. git_repo_cwd = true: Resolves git root from the current file directory (or cwd if no file)

The implementation includes:

• A new claudecode.cwd module with directory resolution helpers
• Support for top-level aliases in the config for convenience
• Working directory resolution at terminal creation time
• Proper passing of cwd to both native terminal and snacks providers
• Comprehensive test coverage for the new functionality

This makes it easier to ensure Claude has the correct context when working with projects, especially in monorepos or when navigating between different parts of a codebase.

[ThomasK33]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat: add focus_after_send option for terminal behavior #118
• feat: add working directory control for Claude terminal #117 👈 (View in Graphite)
• feat: add Shift+Enter keybinding for new line in terminal #116
• feat: add PartialClaudeCodeConfig type for better configuration handling #115
• feat: add option to control behavior when rejecting new file diffs #114
• feat: redesign diff view with horizontal layout and new tab options #111
• feat: add Claude Haiku model and update type annotations #110
• main

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