### Added
- Revert button is now available on the first user message, allowing you to clear the entire conversation and start fresh.
- "Clear Conversation" confirmation dialog shown when reverting from the first message, with distinct messaging from the normal revert dialog.
- Workspace rename: rename any workspace directly from the workspace switcher dropdown via inline editing.
- `@file` mention highlighting: file references selected via `@` autocomplete are now visually highlighted in the chat input with a subtle background tint, and shown as removable chips below the input. Clicking a mention chip opens the file preview dialog.

### Changed
- Preconfig editor: subagent selection now uses a badge-based selector instead of manual text input. Available subagent preconfigs are shown as clickable badges with names and descriptions.
- Preconfig editor: settings JSON textarea replaced with a dedicated temperature number input (0.1–0.9), with validation and clear helper text.
- Preconfig editor: model and provider text inputs replaced with a searchable model selector (grouped by provider) that auto-sets the provider. Variant selector now only appears when the selected model has variants.
- Lowered the compaction message threshold from 4 to 2 non-system messages, allowing compaction after just one user–assistant turn — essential for heavy tool-use sessions.

### Fixed
- Terminal panel is now accessible from any view within a workspace (workspace landing page, overview, etc.), not just when a session is active. Since the terminal is workspace-bound, it no longer requires an active session to be opened.
- Removed aggressive visibility-change reconnect handler that caused unnecessary disconnections and UI flicker when switching tabs or windows. The connection now stays alive through normal tab switches, while dead connections are detected by the new server heartbeat mechanism.
