Fix Common Errors: tweak Step 2 button flow and add fixes-applied counter

[mjuhasz]

Problem

Step 2 of the Fix Common Errors dialog had two UX issues:

Confusing and redundant buttons
The "Apply fixes & close" button was misleading in two ways: its name implied it would apply all fixes, when it actually only applied selected ones — the same as clicking "Apply selected fixes" and then closing. Having both buttons side by side created confusion about which one to use and what each one committed.

The adjacent "Cancel" button added to the confusion: it wasn't clear whether it would discard manually typed edits in the text box, or only the pending (unapplied) fixes in the grid.

No feedback on applied fixes
_totalFixes was already being accumulated in the view model but was never surfaced in the UI, so users had no indication of how many fixes had been applied across multiple "Apply selected fixes" clicks.

Changes

• Replaced "Apply fixes & close" with a "Done" button that simply commits the current state of the subtitle (already-applied fixes + any manual text edits) and closes — no implicit extra apply pass on close. This is how the Subtitle Edit 4 "OK" button behaved.
• "Done" is the intended exit after iterating with "Apply selected fixes". "Cancel" remains as the silent discard path, matching the Subtitle Edit 4 behavior.
• "Done" was chosen over "OK" because the goal was to use descriptive labels that state what happens rather than abstract confirmations. "Apply" was ruled out because it clashes with the "Apply selected fixes" button already in the dialog — it would imply a second apply action is happening on close, which it isn't. "Done" signals "I'm finished with this workflow, close and keep my work" without suggesting any additional processing.
• I kept the lack of warning on Cancel, similar to Subtitle Edit 4 because "Done" is an explicit, deliberate commit action — if the user didn't press it, they haven't committed anything. Cancel's behavior (discard and close) is already implied by the absence of "Done". A warning on Cancel would be noise, not safety.
• Added a "Fixes applied: X" label in the bottom-left corner (using the existing XFixesApplied language string and the existing _totalFixes accumulator). The label appears after the first apply and resets when re-entering Step 2.
• Renamed the buttonApplyFixes local variable to buttonDone to match its new purpose.

[Copilot]

Pull request overview

This PR improves the Step 2 UX of the Fix Common Errors tool by clarifying the dialog’s “exit” action and surfacing how many fixes have been applied during the session.

Changes:

• Replaced the misleading “Apply fixes & close” action with a Step 2 Done button that closes and commits the current state without applying additional fixes.
• Added a Step 2 “Fixes applied: X” label driven by the existing _totalFixes accumulator and XFixesApplied language string.
• Reset the fixes-applied counter/text when entering Step 2.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/ui/Features/Tools/FixCommonErrors/FixCommonErrorsWindow.cs	Renames the Step 2 close action to “Done” and adds a bottom-left “Fixes applied” label bound to the view model.
src/ui/Features/Tools/FixCommonErrors/FixCommonErrorsViewModel.cs	Adds FixesAppliedText, updates it after applying fixes, resets it when entering Step 2, and removes the implicit apply-on-OK behavior.