[Feature request] Exact sync via another subtitle

[lukjak]

This feature handles situations, when you have a subtitle with broken timings and another subtitle (usually in another language) with correct ones.

1. A dialog is displayed like in the "Point sync via another subtitle" (also after requesting selection of a reference subtitle)
2. When a row is selected (in either subtitle), a hotkey causes moving the row and all the subsequent rows one position down, leaving an empty row on one side.
   1. Optionally, the user can enter text in the newly created source rows, select text from existing source rows and edit existing source rows in-place (including deletion). This would allow fast corrections and rows splitting/joining.
   2. Optionally, source rows are color coded, indicating how much "Start time" from the source subtitle row is skewed compared to the corresponding reference subtitle (for example no color for below 0,1s difference, light color below 0,2 difference etc.)
   3. The user can delete a row inserted into the reference file by mistake.
3. Going through the file, user effectively creates sets of paired rows, unpaired rows in the source subtitles and unpaired rows in the reference subtitles.
4. When the user accepts the dialog:
   1. For paired rows, "Start time" is copied from reference subtitle to source subtitle
   2. For unpaired rows, nothing happens

Note: fixing incorrect durations and overlapping display times which can result from the matching are already covered by the existing features.

Note 2: I have tried doing this operation with tools like AutoSubSync and across a few sessions with ChatGPT, with a pair of mostly 1:1 matching subtitles with small timing differences, and the result was completely unusable.

Note 3: This feature is different from "Point sync via another subtitle" in that it allows exact (not approximated) matching from the reference subtitles, which is very important in dialogue-heavy subtitles.