refactor(caret): move active word element offset to test-state and remove .smoothScroller (@NadAlaba)

[NadAlaba]

Description

1. Move activeWordElementOffset to test-state.ts to allow caret.ts to use it without causing circular dependency:

   • Motivation is to determine active word based on logical value, not DOM class, this started on #5834, but didn't continue for caret.ts because it'd cause circular dependency. This move of activeWordElementOffset to test-state.ts would solve the issue.

2. Remove unneeded .smoothScroller:

   • .smoothScoller was only needed to transmit information from test-ui.ts to caret.ts in order to help with caret's vertical positioning during line jump. Now it is replaced by a variable lineScrollDistance in test-state.ts which gets set in test-ui.ts: lineJump() and used in caret.ts.

3. Remove the unnecessary parameter activeWordEmpty from caret.ts: getTargetPositionLeft() and cleanup:

   • Combine the case of (zenMode + RTL + word beginning) with one of the cases of the conditional above it, making the parameter not needed anymore.
   • Also the variable activeWordEmpty in updatePosition() is not needed either, because in zen mode we set wordLen = inputLen, so activeWordEmpty is exactly the same as wordLen === 0.

4. Change variable name from activeWordElementOffset to removedUIWordCount & add a helper function:

   • Also, add a helper function incrementRemovedUIWordCount() to shorten code changing the variable's value.

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: frontend/src/ts/controllers/input-controller.ts

Function	Unhandled Issue
backspaceToPrevious	Error: activeWord is undefined - can't update active element ... Event Count: 4 Affected Users: 4
handleChar	Error: activeWord is undefined - can't update active element ... Event Count: 3 Affected Users: 87

📄 File: frontend/src/ts/test/test-logic.ts (Click to Expand)

Function	Unhandled Issue
init	TypeError: Cannot read properties of null (reading 'style') ... Event Count: 4 Affected Users: 3
init	Error: activeWord is undefined - can't update active element ... Event Count: 2 Affected Users: 9
init	SyntaxError: Invalid left-hand side in assignment / Event Count: 1 Affected Users: 1

📄 File: frontend/src/ts/test/test-ui.ts (Click to Expand)

Function	Unhandled Issue
updateWordsInputPosition	TypeError: Cannot read properties of null (reading 'style') ... Event Count: 146 Affected Users: 121
updateActiveWordLetters	TypeError: Cannot read properties of undefined (reading 'offsetLeft') ... Event Count: 31 Affected Users: 92
updateActiveElement	Error: activeWord is undefined - can't update active element ... Event Count: 16 Affected Users: 87

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[NadAlaba]

after merging #5748 and syncing master, checkout this pr head and:
git rebase --onto master f5f613b
then force push here