feat: Add experimental setting to prevent editor focus disruption

[roomote]

Implements #4784 with the new scoping requirements as clarified by @daniel-lxs.

Summary

This PR adds a new experimental setting "Prevent Editor Focus Disruption" that allows users to disable the diff view entirely when editing files. When enabled:

1. Disables the diff view entirely - Files are edited directly in the background without showing any diff view
2. Edits files directly - All file modifications bypass the diff view and are written directly to disk
3. Preserves diagnostics - The system still captures diagnostics after file changes with a configurable delay
4. No focus stealing - Files are either:
   • Opened without stealing focus (using preserveFocus: true)
   • Not opened at all (when openFile is false)

Changes

• Added new experiment ID PREVENT_FOCUS_DISRUPTION to the experiments system
• Updated experiment types and schemas in the types package
• Added localization entries for the new experimental feature
• Modified DiffViewProvider to add a new saveDirectly method that writes files without showing the diff view
• Updated all file editing tools (writeToFileTool, applyDiffTool, multiApplyDiffTool, searchAndReplaceTool, and insertContentTool) to check for the experimental setting and use direct file saving when enabled
• Added comprehensive tests for the new functionality

Testing

• All existing tests pass
• Added new tests for the saveDirectly method in DiffViewProvider
• Added tests for the new experiment configuration
• Verified that when the experiment is enabled, files are edited without showing the diff view

Fixes #4784

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Important

Adds experimental setting to prevent editor focus disruption by editing files in the background without showing the diff view, with updates to experiments, file editing tools, and localization.

• Behavior:
  • Adds experimental setting "Prevent Editor Focus Disruption" to edit files in the background without showing diff view.
  • Files are edited directly and diagnostics are preserved with a configurable delay.
  • Files can be opened without stealing focus or not opened at all.
• Experiments:
  • Adds PREVENT_FOCUS_DISRUPTION to experiment IDs in experiment.ts.
  • Updates experiment types and schemas.
• File Editing:
  • Modifies DiffViewProvider to include saveDirectly method for direct file writing.
  • Updates applyDiffTool, insertContentTool, multiApplyDiffTool, searchAndReplaceTool, and writeToFileTool to use direct file saving when the experiment is enabled.
• Testing:
  • Adds tests for saveDirectly method in DiffViewProvider.
  • Adds tests for the new experiment configuration.
• Localization:
  • Adds localization entries for the new experimental feature in multiple language files.

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[ellipsis-dev]

The code omission check logic appears in both the experimental and normal branches. Consider refactoring it into a helper function to reduce duplication.

[daniel-lxs]

LGTM

[mrubens]

I like this as an experimental setting! In the future, I wonder if we could add a button or something to preview individual edits as a diff if people want to.

[abumalick]

@daniel-lxs @mrubens What do you think about adding background editing to the auto-approve tab?

Use case

• When vibe coding (auto-write ON): I don’t want the editor to steal focus.
• When reviewing changes before saving (auto-write OFF): I do expect the editor to take focus.

Expected behavior

• Auto-write ON → background editing enabled
• Auto-write OFF → background editing disabled

Proposal

Add a checkbox under Write:

[ ] Automatically activate background editing when auto-approving writes