Use executable bit when completing commands in terminal suggest

[Tyriar]

Part of #285577

[Copilot]

Pull request overview

This PR adds support for the executable bit in the file system API and uses it to filter terminal command completions on Unix-like systems. When completing the first word of a terminal command (the command position), only executable files are now shown as suggestions, improving the relevance of completions.

Key changes:

• Added FilePermission.Executable enum value and corresponding executable field to file stat interfaces
• Updated the disk file system provider to detect executable permissions from Unix file mode bits
• Modified terminal completion service to filter non-executable files when completing commands on Unix systems

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/vs/platform/files/common/files.ts	Added Executable enum value to FilePermission and executable field to IBaseFileStat and IFileStatWithMetadata interfaces
src/vs/platform/files/common/fileService.ts	Updated toFileStat to extract executable permission from stat permissions
src/vs/platform/files/node/diskFileSystemProvider.ts	Implemented detection of executable permission by checking Unix file mode bits (S_IXUSR, S_IXGRP, S_IXOTH)
src/vs/workbench/contrib/terminalContrib/suggest/browser/terminalCompletionService.ts	Added command position detection and executable file filtering logic for Unix systems
src/vs/workbench/api/common/extHostNotebook.ts	Added executable field to file stats returned from notebook save operations
src/vs/workbench/test/common/workbenchTestServices.ts	Updated createFileStat test helper to include executable: false
src/vs/workbench/test/browser/workbenchTestServices.ts	Added executable: false to test file stat mock
src/vs/workbench/services/workingCopy/test/browser/storedFileWorkingCopy.test.ts	Added executable: false to test file stat
src/vs/workbench/services/workingCopy/common/storedFileWorkingCopy.ts	Added executable: false to file stats created in working copy operations
src/vs/workbench/services/textfile/common/textFileEditorModel.ts	Added executable: false to file stats in text file editor model
src/vs/workbench/services/history/test/browser/historyService.test.ts	Added executable: false to test file stat
src/vs/workbench/services/editor/test/browser/editorService.test.ts	Added executable: false to test file stat
src/vs/workbench/contrib/chat/test/electron-browser/tools/builtinTools/fetchPageTool.test.ts	Added executable: false to test file stat

[Tyriar]

@bpasero could you review since I touch a bunch of file service stuff?

[bpasero]

Looks good to me generally, but any chance we could add a test for this to the src/vs/platform/files/test/node/diskFileService.integrationTest.ts suite?. I could think of running it only on POSIX and tampering with the mode on a temporary file and then checking if the relevant executable flag is coming back properly.