Kernel rig: two curvature rounds get 600 s, past the 180 s default, while G2 certification is slow (tangency-labs/smlib#96)

On the CI runners the boss root and the hole rim, both size-2/size-1 curvature rounds, build
correctly but take more than 180 s: the order-2 section's span certificate and the round's
definition are evaluated station by station. The per-case limit is the one the thread cases use.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DtL5M41G8Nua7HvuFPZkmJ

tests/kernel-cases/fillets/cov-fillet-section-curvature-boss-root-r2/expected.json

@@ -11,5 +11,6 @@
  },
  "tolerance": {
   "rel": 1e-07
- }
+ },
+ "timeout_s": 600
 }

tests/kernel-cases/fillets/every-hole-top-rim-r1-curvature/expected.json

@@ -20,5 +20,6 @@
  },
  "continuity": {
   "order": "g2"
- }
+ },
+ "timeout_s": 600
 }