chat-customizations-editor

# Chat Customizations Editor Split-view management pane for AI customization items across workspace, user, extension, and plugin storage. Supports harness-based filtering (Local, Copilot CLI, Claude). ## Spec **`src/vs/sessions/AI_CUSTOMIZATIONS.md`** — always read before making changes, always update after. ## Key Folders | Folder | What | |--------|------| | `src/vs/workbench/contrib/chat/common/` | `ICustomizationHarnessService`, `ISectionOverride`, `IStorageSourceFilter` — shared interfaces and filter helpers | | `src/vs/workbench/contrib/chat/browser/aiCustomization/` | Management editor, list widgets (prompts, MCP, plugins), harness service registration | | `src/vs/sessions/contrib/chat/browser/` | Sessions-window overrides (harness service, workspace service) | | `src/vs/sessions/contrib/sessions/browser/` | Sessions tree view counts and toolbar | When changing harness descriptor interfaces or factory functions, verify both core and sessions registrations compile. ## Key Interfaces - **`IHarnessDescriptor`** — drives all UI behavior declaratively (hidden sections, button overrides, file filters, agent gating). See spec for full field reference. - **`ISectionOverride`** — per-section button customization (command invocation, root file creation, type labels, file extensions). - **`IStorageSourceFilter`** — controls which storage sources and user roots are visible per harness/type. - **`IExternalCustomizationItemProvider`** / **`IExternalCustomizationItem`** — int...