feat: Correctly handle change of cwd automatically and via API

[dmtrKovalenko]

closes #20

This allows to use

require('fff.main').find_files_in_dir('/Users/neogoose/dev/lightsource')

to change cwd and start the picker immediately to choose the file.

[Copilot]

Pull Request Overview

This PR adds functionality to handle changing the current working directory both automatically (via Neovim's DirChanged event) and programmatically through a new API. The changes allow users to reinitialize the file picker with a new directory without having to manually restart the plugin.

• Adds automatic detection of directory changes and re-initializes the file picker accordingly
• Introduces a new find_files_in_dir() API function for programmatic directory switching
• Removes legacy debug code that was no longer needed

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
lua/fff/rust/lib.rs	Adds restart_index_in_path function to reinitialize file picker with new directory
lua/fff/main.lua	Adds autocmd for DirChanged events and new API functions for directory switching
lua/fff/fuzzy.lua	Exposes the new restart_index_in_path function from Rust module

Comments suppressed due to low confidence (2)

lua/fff/rust/lib.rs:49

• [nitpick] The function name reinit_file_picker_internal is ambiguous about what 'internal' means. Consider renaming to reinitialize_file_picker or reset_file_picker_with_path for clarity.

fn reinit_file_picker_internal(path: std::path::PathBuf) -> Result<(), Error> {

lua/fff/main.lua:483

• [nitpick] The function name changed_indexing_directory uses past tense which is confusing for an action function. Consider renaming to change_indexing_directory or set_indexing_directory.

function M.changed_indexing_directory(new_path)