[PierreRaybaut]

Summary

• Store supported desktop plot annotations in Sigima's renderer-independent format shared with DataLab-Web.
• Preserve locked annotations, stable IDs, metadata, extensions, ROI state, and unknown third-party payloads across edits.
• Migrate supported legacy PlotPy payloads only when annotation edits are accepted.
• Cover copy/paste, .dlabann, HDF5 workspace, and remote-control persistence.
• Require Sigima 1.3.0 and SigimaX 1.1.0 or later.

Dependency

• Depends on feat: bridge portable annotations to PlotPy SigimaX#4.

Validation

• 588 passed, 3 skipped
• 21 passed in the focused annotation integration suite
• ruff check .
• ruff format --check . (325 files already formatted)