[RFC] Migrate `src/scripts/` into the layered architecture

## Problem

`src/scripts/` contains 5,513 lines across 6 key files (`app.ts`, `api.ts`, `ui.ts`, `domWidget.ts`, `changeTracker.ts`, `widgets.ts`) that don't fit into the `base → platform → workbench → renderer` hierarchy. `scripts/` imports from stores (5 files), platform (10 files), services (2), composables (4), and renderer (3). It is both a foundation AND a consumer of every other layer — the most-imported module in the codebase.

## Proposed Deepening

Incrementally migrate `scripts/` capabilities into the layered architecture:

| File | Target layer | Rationale |
|------|-------------|-----------|
| `api.ts` | `base/api/` or `platform/api/` | Network layer is foundational |
| `app.ts` | `workbench/` | Orchestrates setup, a workbench concern |
| `ui.ts` | Deprecate | Vue components in `components/` replace remaining usages |
| `domWidget.ts` | `renderer/` | Rendering concern |
| `widgets.ts` | `renderer/` | Rendering concern |
| `changeTracker.ts` | `platform/workflow/` | Workflow change tracking |

## Migration Plan

1. This is a long-term effort that depends on Issues #1 and #2 (ComfyApp/ComfyApi extraction)
2. Move one file at a time with re-exports from the old path for backward compatibility
3. Deprecate the old import paths
4. Remove re-exports once all consumers have migrated

## Testing Strategy

- Backward-compatible re-exports ensure nothing breaks during migration
- `pnpm typecheck` and all tests pass after each move

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11019-RFC-Migrate-src-scripts-into-the-layered-architecture-33e6d73d3650813c95ade519cffc3965) by [Unito](https://www.unito.io)

Start by reading the six key files in src/scripts/—app.ts, api.ts, ui.ts, domWidget.ts, changeTracker.ts, and widgets.ts—and review dependencies on Issues #1 and #2. For any incremental move, preserve old-path re-exports, run pnpm typecheck and all tests, and consider it done only when consumers are migrated without breakage.

Written by the indexing model from the issue text.