H2's ATTACK dynamics, and a construction hazard found while measuring them

The H2 panel measured wins, variance and DARVO but not ATTACK selection —
which is F17's actual question. attack-value now runs H2 too.

The shape is the finding. Under H1 a seat that sometimes attacks loses
everything at 3p and above. Under H2 rank-75 wins 112/173/199 against
greedy's 120/175/199, while attacking and arming DARVO. So H2 makes
occasional ATTACK affordable — it does not make it pay. rank-75 never
beats greedy in any cell, and rank-95 (always attack) still wins 0
everywhere in all three variants, so "not always-attack-optimal" holds.

F17 therefore stands: ATTACK earns its place in no mode. What changed is
that choosing it is no longer catastrophic. Whether affordable is what the
design wants is ground-game's judgement.

And a hazard: with_variant() exists because H2 assigns Problem owners at
setup and `state.variant = v` leaves them unassigned, so scoped pressure
ticks nobody and H2 measures as INERT. Three call sites had the bare
write, including cb-play's driver.

No published figure is affected, and that was checked rather than assumed:
h2-panel used the builder, and the two harnesses with the bare write had
only ever run baseline and H1, neither of which has a setup step; the
driver has never played H2. All three fixed, and
a_bare_variant_write_leaves_h2_inert now states the difference so a
regression is caught by a named test rather than by a reader wondering why
H2 did nothing.

The builder was not enough — the field is public, so the old form still
compiles. Worth knowing before the next variant.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/cb-play/src/table.rs

@@ -408,7 +408,10 @@ fn run_game<'a, R: BufRead + 'a, W: Write + 'a>(
     initial.mode = config.mode;
     // CB-WP-0038: set beside `mode` and before the hash, so a recorded
     // session replays under the variant it was played under.
-    initial.variant = config.variant;
+    // `with_variant`, never a field write: H2 assigns Problem owners at
+    // setup, and the bare write would leave them unassigned — a silently
+    // wrong game rather than a failing one.
+    let initial = initial.with_variant(config.variant);
     let initial_json = serde_json::to_value(&initial).map_err(|e| e.to_string())?;
     let initial_hash = cb_events::state_hash_hex(&initial);