Fix title bar showing *Untitled on startup with no file to reopen

[mjuhasz]

Summary

When launching the app with no recent file to reopen, the title bar incorrectly showed *Untitled — the asterisk that normally indicates unsaved changes — even though nothing had been modified.

Root Cause

_changeSubtitleHash was field-initialized to -1, but GetFastHash() never returns -1 (it computes a hash seeded from 17). The slow timer fires UpdateTitleStatus() shortly after startup and sees _changeSubtitleHash (-1) != GetFastHash(), treating the clean initial state as modified.

_changeSubtitleHash only gets a real value inside ResetSubtitle(), which is called when opening a file or clicking File > New — never during a cold start with no file.

Fix

Seed both _changeSubtitleHash and _changeSubtitleHashOriginal from the actual initial state in the constructor, immediately after SelectedEncoding is set (the encoding is an input to the hash).

SelectedEncoding = Encodings.FirstOrDefault(...) ?? Encodings[0];
_changeSubtitleHash = GetFastHash();
_changeSubtitleHashOriginal = GetFastHashOriginal();

Testing

1. Launch the app with no recent file (or clear recent files first).
2. Verify the title bar shows Untitled - Subtitle Edit x.x with no leading *.
3. Type in a subtitle line and verify * appears.
4. Save and verify * disappears.