feat: add separator, line numbers and view toggle

[shatrughantwt]

Description

Follow-up PR to further enhance the diff viewer with improved layout and usability.

Changes

• Added centered vertical separator
• Implemented properly aligned line numbers
• Added keybinding to toggle between split and unified views
• Unified view remains the fallback below splitViewThreshold

Result

Cleaner split layout, improved readability and better overall user experience.

[bakayu]

feedback from QA:

• The line numbers are too close to the actual text, there should be a gap
• When a line becomes too long (check the screenshot attached) it seems to be wrapping around and breaking the vertical divider
• The color of the divider does not match the color of the panel borders
• You have to press ctrl+d twice while in split diff view mode to change to unified currently, it should only take one click, probably some issue with how the update function was modified
• Also the colors of text in split diff view and unified diff view are not consistent

[shatrughantwt]

feedback from QA:

* The line numbers are too close to the actual text, there should be a gap * When a line becomes too long (check the screenshot attached) it seems to be wrapping around and breaking the vertical divider * The color of the divider does not match the color of the panel borders * You have to press `ctrl`+`d` twice while in split diff view mode to change to unified * Also the colors of text in split diff view and unified diff view are not consistent

okayy. I'll fix it

[shatrughantwt]

help me with the vertical divider issue

[bakayu]

help me with the vertical divider issue

I'll get to this by this weekend.

[bakayu]

The vertical separator still appears broken when the app to see big diffs (tested it on the diffs of this branch)

It works fine for smaller diffs, although there is some spacing issue, I left a comment for it in view.go

[shatrughantwt]

The vertical separator still appears broken when the app to see big diffs (tested it on the diffs of this branch)

It works fine for smaller diffs, although there is some spacing issue, I left a comment for it in view.go

i fixed it. still broken

[bakayu]

could you explain why

The vertical separator still appears broken when the app to see big diffs (tested it on the diffs of this branch)

It works fine for smaller diffs, although there is some spacing issue, I left a comment for it in view.go

i fixed it. still broken

Does it appear not broken in your local? For me it looks broken like in the image I attached.

[shatrughantwt]

i fixed strings.Fields issue after that still shows broken in big diff

[shatrughantwt]

could you explain why

The vertical separator still appears broken when the app to see big diffs (tested it on the diffs of this branch)

It works fine for smaller diffs, although there is some spacing issue, I left a comment for it in view.go

i fixed it. still broken

Does it appear not broken in your local? For me it looks broken like in the image I attached.

it does

[shatrughantwt]

when will you review c9b50ba

[bakayu]

when will you review c9b50ba

I'll get to this by tomorrow!

EDIT: I did a quick QA and looked up the code, its probably that lipgloss's layout management is just not reliable for our usecase. Also, I just noticed github's split view diff when handling soft wrap cap is already similar to ours, so we just need to fix the broken vertical spacer issue. Since you are having trouble with this one I'll try to push a fix for this.

[bakayu]

marking this PR as a draft, split view feature is to be abandoned for now, will look into this later.