refactor: extract file-tree key handling into key_actions module

[sximelon]

Summary

Move the file-tree keyboard event handler (Up/Down/Enter/Esc) out of ui::run_event_loop into a dedicated key_actions module.

The new handle_file_tree_key function returns bool to signal whether the key was consumed, keeping the call site a single-line delegation.

Testing

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features
• cargo test --workspace --all-features

Checklist

• Updated docs or comments as needed
• Added or updated tests where relevant
• Verified TUI behavior manually if UI changes

[gemini-code-assist]

Code Review

This pull request refactors the file-tree keyboard event handling logic into a dedicated key_actions module to improve the maintainability of the main event loop. The review highlights a regression where the omission of the file_tree_visible check causes keyboard events to be intercepted even when the file tree is hidden. Further feedback points out stale documentation referencing an undefined KeyActionResult type and suggests consistent use of inlined variables in format strings.

[gemini-code-assist]

The module documentation refers to KeyActionResult for signaling control-flow changes, but the function currently returns a bool and KeyActionResult is neither defined nor used in this module. This documentation appears to be stale.

[gemini-code-assist]

Inconsistent format string style. Line 44 uses inlined variables (@{path_str}), while line 45 uses positional placeholders (@{} ). It is better to use the inlined style for consistency and to match the original code.

Suggested change

	app.insert_str(&format!("@{} ", path_str));
	app.insert_str(&format!("@{path_str} "));