TJC-1814: use dollar math delimiters in release notes and checklist

RELEASE_CHECKLIST.md

@@ -26,7 +26,7 @@ published.
   and the committed PDF reproduces byte-for-byte.
 - [ ] The supplement is built from the exact tagged commit, its embedded
   manifest verifies, and a second build produces the same archive checksum.
-- [ ] Release notes state the fixed-\(H^{\ast}\) scope, attribute the original
+- [ ] Release notes state the fixed-$H^{\ast}$ scope, attribute the original
   counterexample to D. Rybin, say that global boundedness remains open, and
   retain the “not peer reviewed” label.
 - [ ] The draft GitHub release and all attached artifacts have received a final

RELEASE_NOTES.md

@@ -5,11 +5,11 @@ Research preprint and reproducibility artifact. **Not peer reviewed.**
 ## Result and scope
 
 This release proves the exact worst-case admissible unsplittable-to-fractional
-cost ratio on D. Rybin's fixed seven-vertex digraph \(H^{\ast}\):
+cost ratio on D. Rybin's fixed seven-vertex digraph $H^{\ast}$:
 
-\[
+$$
 \rho(H^{\ast})=\frac{2}{2\sqrt 2-1},
-\]
+$$
 
 as a supremum that is not attained. It does **not** prove a global, planar,
 chain-class, or laned-class upper bound. Global boundedness remains open.