fix format tab size and add detectIndentation for return file tab size

[iskepr]

Description

• Fix tab re-indentation logic: Resolved cursor jumps, double-execution issues, and arithmetic overflow when modifying tab sizes.
• Add detectIndentation(): Implemented auto-detection of the document's actual indentation size based on line diffs.

---

Usage

1. Initialize on File Open

Call detectIndentation() after loading the file content into the controller:

codeController.tabSize = codeController.detectIndentation();
_settings.addListener(_handleSettingsChanged);

2. Handle Settings Changes

Listen to setting updates and safely re-indent the document:

void_handleSettingsChanged() {
final nextTabSize = _settings.get<int>(AppSetting.tabSize); // new TabSize From Settingsif (codeController.tabSize == nextTabSize) return;
WidgetsBinding.instance.addPostFrameCallback(
(_) => codeController.reindentDocument(newTabSize: nextTabSize),
);
}

[heckmon]

I'll review it soon. currently I'm a little bit busy

[iskepr]

Take your time