Refine pathology workspace and extract the headless annotation CLI

[jcwal1516]

Pathology interaction, layer controls, and canvas frame handling now have separate owners. The desktop delegates bounded DICOM metadata parsing to the annotation library, and the headless annotation CLI moves to its own package in that repository.

The change also includes the pending workspace/export fixes, viewport export and presentation updates, Windows application assets/build configuration, the vendored epaint patch, and removal of obsolete execution documents.

Validation on Apple Silicon macOS:

• Locked workspace tests: 350 passed, 2 ignored, using the immutable Git dependency without a local overlay.
• Workspace Clippy with warnings denied, formatting and snapshot diff checks: passed.
• Dependency advisory, source and license policy: passed. MPL-2.0 approval is restricted to dwrote 0.11.5; source/distribution notices accompany the Windows font backend.

The annotation owner is pinned to immutable revision 71851b4a0c286fa9b57326e426962bf1a63a781e, so standalone builds no longer depend on an unpublished registry version. A future crates.io migration remains a separate release step. Manual desktop acceptance and native packaging/signing are not claimed by these checks.

Related owner PR: frames-sg/wsi-dicom-annotations#1