nes: hardcode nextcursorline cursor placement to beforeLine, remove config

[ulugbekna]

Summary

Hardcodes the next-cursor-line prediction cursor placement to BeforeLine (first non-whitespace character of the predicted line) and removes all code supporting the configurable AfterLine alternative.

Changes

• nextCursorLinePrediction.ts — Removed NextCursorLinePredictionCursorPlacement enum, its VALIDATOR, and the now-unused vEnum import.
• configurationService.ts — Removed InlineEditsNextCursorPredictionCursorPlacement (experiment-based setting chat.advanced.inlineEdits.nextCursorPrediction.cursorPlacement) and its import.
• xtabProvider.ts — Dropped the config read and switch statement; getNextCursorColumn(line) now unconditionally returns the column of the first non-whitespace character.
• xtabProvider.spec.ts — Removed AfterLine test cases and the placement parameter from colWithMarker; kept the BeforeLine cases (renamed without prefix).

Testing

• Type-check (npx tsgo --noEmit --project tsconfig.json and tsconfig.worker.json): ✅
• xtabProvider.spec.ts (176 tests): ✅

[Copilot]

Pull request overview

Hardcodes next-cursor-line prediction cursor placement to BeforeLine (first non-whitespace character) across the Copilot inline edits “xtab” flow, and removes the experiment/config plumbing for the previously supported AfterLine alternative.

Changes:

• Removed NextCursorLinePredictionCursorPlacement and its validator from the shared inline-edits data types.
• Removed the experiment-based setting chat.advanced.inlineEdits.nextCursorPrediction.cursorPlacement from the Copilot configuration service.
• Simplified XtabProvider.getNextCursorColumn(...) and updated tests to cover only the hardcoded BeforeLine behavior.

Show a summary per file

File	Description
extensions/copilot/src/platform/inlineEdits/common/dataTypes/nextCursorLinePrediction.ts	Removes the cursor placement enum + validator now that placement is no longer configurable.
extensions/copilot/src/platform/configuration/common/configurationService.ts	Drops the experiment-based config key and associated import.
extensions/copilot/src/extension/xtab/node/xtabProvider.ts	Removes config read/switch; always computes cursor column as first non-whitespace.
extensions/copilot/src/extension/xtab/test/node/xtabProvider.spec.ts	Removes AfterLine test cases and updates helpers to match the new API.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 0