VERTEX (2D) reads its tangent only when flag 0x02 is set; §20.4.11's own R14 example needs it unconditionally #272

Spec: §20.4.11 VERTEX (2D) (10), p114: Flags EC, Point 3BD, Start width BD, End width BD ("Not present if the start width is < 0.0"), Bulge BD, R2010+ Vertex ID BL, then, for every release, Tangent dir BD.

Finding

The spec's own R14 example, §20.4.11.1 (p115, OBJECT: pline vert (AH), len 22H (34), handle: 4D), closes exactly on its §20.4.1 RL boundary under that list: flags 0, point (2, 2, 0), start width 0.0, end width 0.0, bulge 0.0, tangent dir 0.0. The record's printed CRC verifies (CRC-8, seed 0xC0C1), so these are the bytes AutoCAD wrote.

entities::vertex::decode reads the tangent only when flag & 0x02 is set, so on this record (flags 0) it stops one BD short:

VERTEX_2D data fields ended at bit 221, data stream ends at 223 (delta -2)

It also always reads End width, where §20.4.11 omits it when Start width is negative. The example does not exercise that branch (its start width is 0.0).

No type-0x0A record is in the local 19-file corpus (the ten VERTEX records of sample_AC1032.dwg are 3D and PFACE vertices), so the closes state of §20.4.11 in docs/spec-coverage.md should be re-checked against the pinned CI corpus.

Reproduce

cargo run --release --example spec_examples

Row 20.4.11 of tests/fixtures/spec-examples/r14-objects.tsv (#107).

Acceptance

• The §20.4.11.1 row closes, and its expect cell becomes closes.
• No corpus record that closes today stops closing.