cmux-next: New Tab tabs draw the new-tab icon, not the agent chat bubble
Summary
Fixes item 15 of the cmux-next sweep (cmuxterm-hq#1421): Agent tabs and New Tab tabs shared the generic chat bubble. Both ride a conversation record, and TabItemMapping gave every conversation tab agent.chat.
The pane already knows which tabs are still on the New Tab page (AgentTabs.pageTabs), since it titles them "New Tab". It now passes that to the mapping, and those tabs draw the registry's tab.new.
| Tab | Was | Now |
|---|---|---|
| New Tab page | agent.chat | tab.new |
| Agent chat with a known harness | harness mark | harness mark (unchanged) |
| Agent chat without a harness mark | agent.chat | agent.chat (unchanged) |
Converted call sites:
TabItemMapping.item(_:fallbackTitle:isNewTabPage:): newisNewTabPageflag, defaultfalse.PaneController.snapshot(): computesisNewTabPageonce and uses it for both the title and the icon.
When a New Tab page becomes a chat, its title and icon change in the same snapshot.
Not changed:
- Workspace-row kind icons. They are pending Leo's call.
- The sidebar's tab list. It doesn't know which tabs are New Tab pages (it also titles them from the record), so it keeps
agent.chatfor them. Follow-up: giveSidebarTabKinda new-tab case once the sidebar gets that state.
Testing
Red commit d6ea400baef adds ConversationTabItemTests.aNewTabPageTabDrawsTheNewTabIcon; the fix follows. The same conversation record maps to tab.new as a New Tab page and to agent.chat as a chat.
Changelog
Fixed: New Tab tabs show a new-tab icon instead of the agent chat bubble
Demo Video
Fleet builds of base (ff267c4b41d) and the fix, on a capture mini (1x display), opening a workspace's first New Tab.
New Tab tab at 6x, before (top) and after (bottom):
| Before | After |
|---|---|
 |  |
Checklist
- Behavior changes have added or updated tests, or Testing says why not
- UI change with no new or changed user-facing strings; localization not affected
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