refactor: extract inpainting services

[provos]

Summary

• extract mask, prompt, model, candidate, apply/erase, and slice-version workflows into a framework-neutral InpaintingService
• reduce Dash callbacks to transport, rendering, logging, and PreventUpdate adapters
• fix candidate generation mutation, stale selection, pipeline/upscaler invalidation, and duplicate erase logging
• add deterministic Playwright coverage for Fill, Enhance, Erase, Undo/Redo, and prompt persistence

Verification

• 252 Python tests passed
• 11 Playwright tests passed
• Black and focused flake8 clean
• git diff --check clean
• independent review found no remaining P1/P2 issues

[Copilot]

Pull request overview

This PR refactors the web UI inpainting workflow by extracting inpainting state mutation, artifact persistence, candidate generation, and slice versioning into a framework-neutral InpaintingService, leaving Dash callbacks as thin adapters for transport, rendering, and PreventUpdate control flow.

Changes:

• Introduces parallax_maker/inpainting_services.py with command/result dataclasses and an InpaintingService orchestration layer.
• Refactors Dash callback adapters in components.py and webui.py to call the service instead of mutating AppState directly.
• Adds new Python adapter/service contract tests and extends Playwright E2E coverage for inpainting behaviors (Fill/Enhance/Erase/Undo-Redo/prompt persistence).

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
parallax_maker/webui.py	Wires a shared InpaintingService into callback registration and routes prompt/model/undo/selection adapters through the service.
parallax_maker/components.py	Reworks inpainting + canvas callbacks to translate UI transport into service commands and map domain errors to Dash control flow/logs.
parallax_maker/inpainting_services.py	Adds the framework-neutral inpainting workflow service, including mask/workflow artifacts, pipeline reuse, candidate generation, and slice versioning.
parallax_maker/e2e_server.py	Extends E2E state payload with slice filenames for deterministic browser assertions.
parallax_maker/test_components.py	Updates component tests to construct callbacks with an InpaintingService and artifact/pipeline stubs.
parallax_maker/test_inpainting_webui_adapters.py	Adds unit coverage for webui.py inpainting adapter callbacks and their error→PreventUpdate mapping.
parallax_maker/test_inpainting_services.py	Adds contract tests for the new service’s behaviors (mask, prompts/model persistence, generation, apply/erase, undo/redo).
parallax_maker/test_inpainting_component_adapters.py	Adds contract tests for Dash callback adapters around the service boundary.
e2e/parallax-maker.spec.ts	Expands Playwright coverage for fill/enhance/erase flows, undo/redo, and prompt persistence.
e2e/helpers/app.ts	Adds helper utilities + extends E2EState typing for new assertions.

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