feat - support edit/create local files outside of workspace

[xinyi-gong]

Summary

• Add support for create_file and edit_file tool when the target is an absolute local file path outside the Eclipse workspace.
• Track local file changes in the file change summary bar alongside workspace files.
• Support local file View Diff, Keep, and Undo flows, including empty-baseline diffs for newly created files.
• Preserve existing workspace-file behavior by resolving Eclipse IFile resources before falling back to local filesystem paths.
• Add focused unit coverage for local create/edit paths and a SWTBot markdown test plan for the user-visible local file flows.

[Copilot]

Pull request overview

Adds support for tracking and reviewing create_file / insert_edit_into_file operations targeting absolute local filesystem paths outside the Eclipse workspace, integrating them into the existing “file change summary bar” UX and diff/keep/undo flows.

Changes:

• Introduces a ChangedFile abstraction so the summary bar can track both workspace IFile and external Path targets.
• Extends Create/Edit file tools and the compare-editor plumbing to support local files (including empty-baseline diffs for newly created files).
• Adds/updates unit tests and documents a SWTBot test plan for the user-visible local-file flows.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/WorkingSetBar.java	Updates summary bar UI to render and route actions for ChangedFile (workspace + local).
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/WorkingSetHandler.java	Extends handler contract with Path overloads for keep/undo/view-diff.
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/FileToolService.java	Switches change tracking to ChangedFile, adds routing for local keep/undo/diff and “created then edited” behavior.
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/FileToolBase.java	Adds local-file caches and compare editor handling (Path-keyed) alongside existing workspace support.
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/EditFileTool.java	Adds local-path resolution + local edit/write/undo/diff behavior.
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/EditableLocalFileCompareInput.java	New compare input to represent editable local-file content within Compare UI.
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/CreateFileTool.java	Adds local file creation + local diff/undo support; adjusts baseline caching for create flows.
com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/tools/ChangedFile.java	New model type representing either a workspace IFile or external local Path.
com.microsoft.copilot.eclipse.ui.test/src/com/microsoft/copilot/eclipse/ui/chat/WorkingSetBarTest.java	Updates UI unit tests to use ChangedFile for summary bar rendering scenarios.
com.microsoft.copilot.eclipse.ui.test/src/com/microsoft/copilot/eclipse/ui/chat/tools/EditFileToolTest.java	Adds focused unit coverage for external local-file edit and undo/baseline behavior.
com.microsoft.copilot.eclipse.ui.test/src/com/microsoft/copilot/eclipse/ui/chat/tools/CreateFileToolTest.java	Adds focused unit coverage for external local-file create and undo behavior.
com.microsoft.copilot.eclipse.swtbot.test/test-plans/file-system/local-file-edit-and-create-tools.md	Adds a SWTBot-oriented manual test plan for local file edit/create UX flows.