[FEATURE] Allow relocating a Cowork project's primary folder without losing project data

### Preflight Checklist

- [x] I have searched [existing requests](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20label%3Aenhancement) and this feature hasn't been requested yet
- [x] This is a single feature request (not multiple features)

### Problem Statement

In Cowork, once a project is created from a folder, that original folder is permanently bound as the project's primary location. Additional folders can be attached afterward, but there's no way to move, replace, or re-link the original one.

If that folder needs to relocate on disk (reorganizing files, renaming a directory, cleaning up a Downloads folder, etc.), the only current option is abandoning the project entirely and starting a new one from scratch. That loses the project's accumulated memory/notes, saved instructions, and full conversation/session history.

This is a normal, expected part of file organization, and today it forces a costly tradeoff between reorganizing files and preserving everything the project has built up.

### Proposed Solution

Add a way to change a Cowork project's primary folder to a new location while preserving everything else tied to the project (memory, instructions, history). This could work either way:

1. A manual "re-link primary folder" action in project settings, where the user points the project at the new folder path.
2. Automatic detection: storing a project identifier inside the folder itself, so if the folder is moved or renamed, Cowork can recognize it at its new path and reconnect automatically.

### Alternative Solutions

The only current workaround is to abandon the project entirely and start a brand-new Cowork project pointed at the new folder location, then manually try to recreate or re-paste over any project memory, instructions, and context that mattered from the old project.

### Priority

High - Significant impact on productivity

### Feature Category

Configuration and settings

### Use Case Example

_No response_

### Additional Context

Related: issue #33636 covers the underlying bug where moving/renaming a folder orphans Claude Code sessions generally. This request is the feature-level fix specific to Cowork projects: a supported way to relocate the primary folder, since Cowork projects accumulate meaningful memory/context that shouldn't be lost over routine file housekeeping.

No files or tests are identified. Start by locating Cowork project settings and the code that stores the primary folder association, then trace how project memory, instructions, and session history are persisted. Done means a moved or renamed primary folder can be re-linked or detected without losing that project data.

Written by the indexing model from the issue text.