Rename Agent chats and sessions to tasks in user-facing UI

[marksftw]

Summary

Use task terminology consistently throughout Agent mode while keeping chat terminology unchanged in Chat mode. Internal implementation names such as “session” do not need to change unless they are user-facing.

Terminology rules

Context	Chat mode	Agent mode
Primary item	Chat	Task
Create action	New Chat	New Task
Collection/history	Chats / Chat history	Tasks / Task history
Untitled placeholder	New chat	New task
Destructive action	Delete chat	Delete task
Current item references	This chat	This task

The mode itself remains named Agent, including the Chat | Agent mode switch.

Scope

Audit and update all user-facing Agent-mode strings, including:

• Sidebar actions, headings, history lists, and empty states
• New-item flows and untitled placeholders
• Context menus and command-menu entries
• Delete confirmations and other dialogs
• Search, filter, and navigation labels
• Status, error, retry, and completion messages
• Toasts and notifications
• Tooltips, keyboard shortcut descriptions, and accessibility labels
• Settings or help text that refers specifically to Agent-mode items

Use task for the durable unit in Agent history. Avoid exposing session as a synonym for that unit.

Compatibility and behavior

• Existing Agent history remains intact and appears as tasks after the terminology change.
• Legacy untitled Agent items display New task rather than an old chat/session placeholder.
• Existing generated or user-authored titles are not rewritten.
• Chat mode retains its current chat terminology.
• This is a user-facing language change only; routes, storage, types, and internal session concepts may remain unchanged.
• Wording that intentionally compares both modes may use both terms, such as “Chats and tasks are kept separate.”

Acceptance criteria

• Creating an item in Agent mode is labeled New Task.
• Agent history and Agent item actions consistently use task/tasks.
• Delete and confirmation flows identify the affected item as a task.
• Empty, loading, error, retry, and completion states use task-appropriate language.
• Tooltips and assistive-technology labels match the visible terminology.
• Existing Agent items continue to load normally and are presented as tasks.
• Chat-mode UI remains unchanged.
• No user-facing chat or session references remain in Agent-only UI, except user-authored content or deliberate cross-mode explanations.

Out of scope

• The Chat | Agent switch component, which is tracked separately.
• Renaming internal session models, APIs, database fields, or routes.
• Combining Chat and Agent histories.
• Changing generated/user-authored task titles.