--resume should show the most recent sessions first and support filtering

### Describe the feature or problem you'd like to solve

Starting copilot with --resume shows not only the "most recent" instead it shows "this branch" or any other very old session unless one scrolls don to "this folder"

### Proposed solution

The whole `--resume` workflow becomes cumbersome when there are more than an handful sessions.

Especially when one installs an update with `/update` and then restart its completely hard to find the just a few minutes/seconds ago started session in the flood.

One would expect that "this branch" will show it on top but that not the case.. sometimes its hidden in "this folder" and instead showing very old sessions on the top instead.

My proposal would be:

1. Have a new category "Most recent" showing the 5 most recently used sessions
2. Have some kind of filtering support instead of only a long list

### Example prompts or workflows

_No response_

### Additional context

_No response_

Start at the CLI entry point for the --resume workflow and trace how sessions are grouped and ordered. Define how a Most recent category should select five sessions and how filtering should interact with the existing list; done means recent sessions appear predictably and users can narrow the session list.

Written by the indexing model from the issue text.