docs: preview modernized dj.Diagram style on the LC-MS pipeline

[dimitri-yatsenko]

Draft — for visual review only. Regenerates docs/pipeline.svg (the README diagram) using the restyled dj.Diagram from datajoint/datajoint-python#1534 (issue #1532), so the new diagram style can be seen against a real pipeline.

The regenerated diagram shows:

• the modern tier palette (Manual green, Lookup gray rectangle, Imported/Computed ellipses, near-white part boxes),
• master–part entity clustering with prefix-dropped part labels,
• rounded nodes + schema cluster,
• the corrected edge-weight = cardinality rule (thick = 1:1, thin = multi-valued),
• Helvetica typography.

Rendered against datajoint/lcms-demo@main's schema with a pre-release build of dj from #1534. Not for merge until #1534 is released; opening as a draft so the README preview renders the new diagram for review.

[dimitri-yatsenko]

Re-ran against datajoint/datajoint-python@master (2.3.3.dev16+g8e6ef316) now that #1534 has merged — docs/pipeline.svg regenerated in 58c9ed8.

Regenerating against master also picks up the two diagram changes that landed after #1534:

• #1544 — the DataJoint brand tier colors in the diagram themes (visible here as green Manual, gray Lookup, blue Imported, orange Computed).
• #1545 — collapsed-to-collapsed edges no longer carry per-foreign-key style.

Everything the original preview was opened to show still holds: master–part entity clustering with prefix-dropped part labels (Scan, Spectrum, Peak), rounded nodes, schema clusters with top-right labels, and edge weight encoding cardinality.

Still a draft: #1534 merged after v2.3.2, so the style is unreleased and pyproject.toml's datajoint[postgres]>=2.3.0 does not yet pin a version that produces this diagram. Ready to mark for merge once the release lands.

One rough edge worth a separate issue upstream: Diagram.save() on an .svg path imports IPython (via make_svg), so saving a diagram to a file fails in a plain non-notebook environment unless IPython is installed.