Add post-apply diff review UI (Keep/Undo per file, like GitHub Copilot Chat)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Currently, Claude Code's VS Code extension only supports pre-apply diff review: Claude shows a diff and asks for approve/reject before the edit is applied (in default permission mode), or shows the whole plan upfront in plan mode. There's no way to let changes apply immediately and then review/curate them afterward.

This makes review uncomfortable for multi-file turns — you either have to interrupt the flow to approve every single edit one-by-one, or approve a whole plan blind and then manually diff each file yourself with no dedicated UI for it.

Environment

• Claude Code VS Code extension (native)

Proposed Solution

Support a workflow similar to GitHub Copilot Chat's post-apply review:

1. Claude applies its changes for the turn immediately (no per-edit interruption).
2. A "Changes" list appears (sidebar or panel) showing every file touched in the turn.
3. Clicking a file opens a proper side-by-side diff view for just that file.
4. Each file (or ideally each hunk) has Keep / Undo actions, so I can selectively accept some changes and revert others without reverting the whole conversation/checkpoint.

Why this matters

• Reviewing diffs interruption-by-interruption during generation is disruptive to flow.
• The existing alternatives don't cover this:
• plan mode batches approval into one step, but it's still pre-apply, all-or-nothing.
• The desktop app's diff viewer (+12 -1 indicator) is read-only — no accept/reject actions.
• Checkpoints let you rewind, but only to whole conversation states, not per-file.
• A post-apply, per-file/hunk keep-or-undo UI would make reviewing large multi-file changes much faster and less disruptive, especially for people used to Copilot's review flow.

Alternative Solutions

_No response_

Priority

Critical - Blocking my work

Feature Category

Interactive mode (TUI)

Use Case Example

_No response_

Additional Context

_No response_