Add a DNF row head to head, and stop bailing out one scenario early

[dgoodenough]

Follow-up to #76. The head-to-head ladder ran to the back of the field, which is not the bottom of what can happen to the leader: every finishing place pays something, and not finishing pays nothing.

The row

A DNF now sits under last place, ruled off from the ladder because it is an outcome rather than a position:

  Tamm finishes   Ends on   Klein needs   Margin
  80th            741.77    68th          12 ahead
  81st            740.1     72nd          9 ahead
  ──────────────────────────────────────────────────
  DNF             730.1     any           —

The leader ends on exactly what they have banked. The margin column reads —, because there is no place to be ahead of.

The bug it exposed

The panel skips the table and prints a sentence when the lead is more than the event can pay. It decided that by asking whether the chaser could be caught at the leader's worst finish — and that is a different claim from "cannot be caught at all", because the back of the MPO field still pays 10 points.

A leader parked between the chaser's ceiling and the chaser's ceiling plus a last-place finish therefore could not be passed at any place on the curve, and could still be passed on a DNF. The panel bailed out of a table whose DNF row would have shown a real answer.

Reproduced directly by parking a leader inside that window:

leader 1006.3 pts · chaser's ceiling 1011.3 · last place pays 10

  1st    1,256.33   —     —
  ...
  81st   1,016.33   —     —     <- every finishing place out of reach
  DNF    1,006.33   1st   —     <- but a DNF leaves a route

Before this change that rendered no table at all, just "cannot pass them there however the weekend goes" — which was false.

It now tests against the DNF total, the actual floor. Two copy changes fall out of that:

• The sentence for a lead nothing can close says so out loud: "…cannot pass them there however the weekend goes, even if Tamm does not finish."
• The narrower case gets its own line, where every finishing place settles it but a DNF does not: "Any finish at all from Marwede settles it — a DNF is the only thing that leaves Ulibarri a route."

Verification

• 82 rows in MPO, 43 in FPO; DNF row reads DNF | 730.1 | any | — (MPO) and DNF | 963.58 | 33rd | — (FPO).
• Both divisions at 390px and 1180px, every tab walked and returned to: no page errors, no horizontal overflow.
• The previously-wrong branch exercised directly by mutating a leader's points into the window: every place —, DNF row 1st, table rendered where the old code rendered none.
• python -m pytest tests -q → 258 passed (unchanged — this touches no Python).

🤖 Generated with Claude Code

https://claude.ai/code/session_01JsBC4pyUqbxW9y5o9tAeRr

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