render: provide an explicit native sequence notation projection #6

Weaver is removing its raw D2 SVG renderer and uses the public functional pipeline exclusively. Four existing sequence views (admission, consume timeout, late claim, committed dispatch) cannot yet migrate without changing their notation or filtering generated lifelines.

The current upstream model-adaptation.test.ts already preserves this counterexample:

shape: sequence_diagram
a -> b: message

compileModel retains three native relations, two ending at SDK-generated lifeline endpoints absent from the subject inventory. graphFromModel correctly refuses the graph. Filtering names, guessing ownership from dotted IDs, flattening to another notation, or returning raw D2 geometry would defeat the source-fidelity contract.

Please provide an explicit public sequence-notation projection/composer backed by native SDK observations. It should retain actor identities, ordered messages, self-calls, notes and ownership; separately represent drawing-only lifeline anchors; use actual font measurements and vector glyphs; and preserve source/projection trace in standalone SVG provenance. Unsupported groups or endpoint forms should refuse explicitly. Include negative controls for real dashed/empty-label messages, generated-looking user names, nested spans, duplicate labels and reversed endpoints.

Until that capability exists, Weaver retains the four sources/artifacts and records complete-catalog acceptance as FAIL. It has no legacy renderer fallback. The other declarations use public measured model views. This is a notation capability request, separate from the compiler allocation-lifetime fix in PR #5.