[FEATURE] Cowork on macOS: add message-level Edit and Retry/Regenerate parity with normal 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

In Claude Desktop on macOS, the normal chat UI supports message-level actions like:

• retry/regenerate a response (refresh icon)
• edit a previous user message and branch from that point (edit/pencil icon)

<img width="266" height="105" alt="Image" src="https://github.com/user-attachments/assets/142f8358-9a8a-4b3b-ae3e-e0ecee7b950a" />

In Cowork sessions, these actions are not available. This blocks an important workflow: quickly retrying or rewriting earlier turns without manually re-creating context.

Proposed Solution

Add message-level action parity in Cowork with normal Claude chat on macOS:

1. Show Retry/Regenerate action for assistant responses.
2. Show Edit action for prior user messages.
3. When editing an older user message, branch/resume conversation from that message point (same behavior as normal chat).
4. Keep behavior consistent with existing normal-chat UX so users can move between chat and Cowork without learning different interaction patterns.

Alternative Solutions

Current workaround is to copy/paste older prompts and manually restate context in a new message. This is slower and often produces less accurate follow-ups versus true branch-from-history editing.

Priority

High - Significant impact on productivity

Feature Category

Other

Use Case Example

1. I ask Cowork to analyze a codebase and it returns a long answer.
2. I want a different approach from the same earlier prompt.
3. In normal chat I would click refresh/regenerate, or edit my older message and re-run from there.
4. In Cowork I cannot do either, so I must rewrite prompts manually and lose fast iteration.

Additional Context

• Platform: macOS
• Claude Code version: 2.1.41
• This is specifically about Cowork UI parity with normal Claude chat message actions.
• I have a screenshot showing the normal chat icons (refresh and edit) that are missing in Cowork; I can add it in a follow-up comment if needed.