fix: agent host confirmation creation

[justschen]

fix #323262

fix bug where confirmation sub part's pill did contain the right metadata

[Copilot]

Pull request overview

This PR fixes issue #323262, where a pending file-creation confirmation (e.g. the agent creating package.json) rendered a file pill that opened an error instead of a preview of the proposed content. The root cause was that the confirmation sub-part's pill lost the "create" metadata and proposed-content URI, so clicking it tried to open a non-existent file. The fix threads a new editKind through the state→progress adapter and confirmation data, distinguishes "Create file?" vs "Write file?" in the permission display, and routes pill clicks through a shared editor-input builder so created files preview as an empty→proposed diff.

Changes:

• Derive whether a write permission targets a new file (isNewFile) and surface distinct "Create file?" wording plus a Creating … invocation message, carrying editKind into IChatModifiedFilesConfirmationData.
• Centralize preview-editor-input creation (createModifiedFilePreviewEditorInput) and summary labels (getModifiedFilesSummaryLabel), and let inline anchor pills use a custom openResource callback so confirmation-message links preview the pending change.
• Restore single external-edit pills to their original parent in the thinking content part, and add tests across the affected layers.

Show a summary per file

File	Description
copilotAgentSession.ts	Computes isNewFile from built edits and passes it to getPermissionDisplay.
copilotToolDisplay.ts	Adds isNewFile param to emit Create-vs-Write title and invocation message.
stateToProgressAdapter.ts	Propagates edit.kind into modifiedFiles[].editKind (missing as ChatExternalEditKind cast — see comment).
chatService.ts	Adds optional editKind to IChatModifiedFilesConfirmationData.modifiedFiles.
chatModifiedFilesConfirmationSubPart.ts	New helpers for entry lookup, summary label, and preview-input creation; wires pill clicks to openModifiedFilePreview.
chatInlineAnchorWidget.ts	Adds openResource option and hoists editor-option computation before the override path.
chatMarkdownDecorationsRenderer.ts	Passes the new options argument to InlineAnchorWidget.
chatThinkingContentPart.ts	Adds restoreToOriginalParent so external-edit pills restore correctly.
copilotAgentSession.test.ts	Fake IFileService gains exists/writeFile/del; new create-wording test.
copilotToolDisplay.test.ts	Tests create-vs-edit write permission display.
stateToProgressAdapter.test.ts	Tests editKind/proposed-content mapping for pending create confirmations.
chatModifiedFilesConfirmationSubPart.test.ts	New unit tests for the extracted helpers.
chatInlineAnchorWidget.test.ts	Tests the custom openResource opener path.
chatThinkingContentPart.test.ts	Tests external-edit pill restoration beside a hidden tool invocation.

Review details

• Files reviewed: 14/14 changed files
• Comments generated: 1
• Review effort level: Medium