Withdraw the double-shaft edge glyph — both variants rejected live

The converged variant read as two arrows feeding one point; the two-
complete-arrows variant as two arrows next to each other, not coherent.
Owner withdrew the double-shaft idea entirely (2026-09-15); dashed was
already rejected 2026-09-14. Both relation types draw the same plain
single arrow again.

Kept: CanvasEdge.type plumbing from the snapshot (the next
differentiator will need it) and the ArrowGeom named type. Removed:
followsEdgeGeometry, the gap constants, the zoom-drift edge-path
rebuild (edges are back to a single loop in buildGeometry), the ⟹
legend entry, and the glyph tests. Vision doc records the withdrawal
and keeps the still-valid constraints.

Gates: tsc, 429/429 tests, lint, build. Live: canvas coverage 0.477,
no console errors, no legend remnants.

components/graph-view.tsx

@@ -896,19 +896,6 @@ export function GraphView() {
 				</div>
 			)}
 
-			{/* Edge glyph legend (bottom-right; the pipeline status pills own
-			    the bottom-left). ⟹ follows (the derivation backbone) · →
-			    supports — DECIDED 2026-09-14, docs/vision-edge-glyph.md. */}
-			{!isEmpty && (
-				<div className="pointer-events-none absolute bottom-3 right-3 z-10 flex items-center gap-2 rounded-full border bg-card/85 px-3 py-1.5 text-xs text-muted-foreground shadow-lg backdrop-blur">
-				<span className="font-medium text-foreground">⟹</span>
-				<span>follows</span>
-				<span className="text-muted-foreground/60">·</span>
-				<span className="font-medium text-foreground">→</span>
-				<span>supports</span>
-			</div>
-			)}
-
 			{/* Background pipeline status: what is currently running. */}
 			{pipelineRuns.length > 0 && (
 				<div className="absolute bottom-3 left-3 z-10 flex flex-col gap-1.5">