Add deterministic visual authoring independence regressions

[multiplex55]

Motivation

• Ensure the Action Editor preserves independence between search-region editing and reference-image capture by exercising the full VisualCaptureWorkflow inside a real ActionEditorState fixture so terminal outcomes are restored and applied only through the normal editor paths.
• Make the authoring workflows fully testable and deterministic (no sleeps, no real overlays, no real screen/file access) so regressions around capture, staging, cancellation and stale tokens are reliably detected.

Description

• Add a fake-backed full-editor fixture and a suite of deterministic tests that install a real VisualCaptureWorkflow into ActionEditorState with fake VisibilityAdapter, WorkflowClock, RectangleOverlay, CaptureAdapter, and AssetStoreAdapter.
• Add tests covering Pick Region success, Reference Image Capture success, capture cancellation at two useful points, capture downstream failures (capture and staging), and a stale-token variant that must be ignored while launcher restoration still occurs.
• Initialize scenarios with a known macro id and draft generation, an initial MkImagePayload containing asset_id = 7 and SearchRegion::Rectangle { rect: ScreenRect::new(100,100,800,600) }, and snapshot/clone unrelated payload fields before operations to assert they remain unchanged.
• Make ImageSearchEditorState comparable by deriving PartialEq/Eq to enable byte-for-byte or field-for-field equality assertions in cancellation and stale-token tests.

Testing

• git diff --check was run and passed for the patch format.
• cargo test visual_authoring_independence --lib was invoked; compilation progressed but a full run is blocked on platform-specific unconditional Windows API imports when building on Linux (the test logic itself is platform-agnostic and uses the fake adapters).
• Repository formatting checks were performed (rustfmt/cargo fmt) and modified files were formatted as part of the change.

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Codex Task