Remove broken round-polygon shapes from the picker and coerce stored values

[kmcginnes]

Description

Cytoscape's round-polygon renderer degenerates at the 24px node size used on the canvas for six shapes (round-triangle, round-pentagon, round-hexagon, round-heptagon, round-octagon, round-tag): the fill renders as a blob and the edge-intersection computation returns no valid point, so connected edges disappear. These shapes became selectable via #1886; no upstream cytoscape fix exists (3.34.0 is latest).

This PR removes the six shapes from the picker and coerces any previously stored value to its non-round counterpart at the read boundary, preserving the user's visual-differentiation intent:

Broken shape	Coerced to
round-triangle	triangle
round-pentagon	pentagon
round-hexagon	hexagon
round-heptagon	heptagon
round-octagon	octagon
round-tag	tag

• Picker — the six shapes are removed from NODE_SHAPE.
• Storage edge — a ReadTransform on the user-vertex-styles and shared-vertex-styles atoms coerces stored broken shapes at load time (never writes back, so originals are recoverable if cytoscape fixes the bug).
• Import — stores the value as-is; the ReadTransform coerces on next load, keeping the import path non-destructive.
• SHAPE_STYLES stays inclusive — the six values remain in the enum and ShapeStyle type, so older styling files still parse cleanly.

How to read

1. vertexStylesTransform.ts — the per-shape mapping, coerceBrokenShape(), and the ReadTransform
2. storageAtoms.ts — wires the transform onto the two vertex-styles atoms
3. nodeShape.ts — picker list trimmed
4. vertexStylesTransform.test.ts — unit + backward-compat integration tests
5. ADR — documents the coerce-vs-reject decision and reversal condition
6. ReadTransform ADR update — notes this as the second consumer

Validation

• pnpm check:types and pnpm check:format pass.
• pnpm test passes — 2128 tests across 185 files.
• Backward-compat integration tests prove the full localForage → atom pipeline coerces correctly and does not write back.

Related Issues

• Closes Round polygon node shapes render incorrectly on the canvas and cause edges to disappear #1922
• Closes Round polygon node shapes render incorrectly on the canvas and cause edges to disappear #1921
• Related to Rename styling vocabulary to Styles and reshape style types #1886, Combine node and edge styling into one Styles sidebar #1914

Check List

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I have verified pnpm checks passes with no errors.
• I have verified pnpm test passes with no failures.
• I have covered new added functionality with unit tests if necessary.
• I have updated documentation if necessary.