Stage 21 addendum: the second frozen pairing disagrees with the first

Receipts finished filling before the chains stopped (1,093 scored cells,
up from 881). The extra rows are all post-drift, so the first pinned
subset is unchanged, but the later schemas now form a second and larger
internally-consistent pairing - legacy 2671ch x address 5031ch, the
CURRENT definitions on the tree, paired n=186 asis.

It disagrees with the first. f1_best +0.0231 [0.0070, 0.0426] becomes
+0.0013 [-0.0211, 0.0269]; reached_by_read +0.1000 [0.0200, 0.1827]
becomes -0.0269 [-0.0867, 0.0391]. Neither pairing's f1_best clears its
within-arm replicate floor, so the honest reading of both together is
no demonstrated quality effect, and the early positive is a small-n
fluctuation rather than something a later revision erased.

Corrects the correction: it said the disqualification trigger does not
fire on the registered arms. That holds for the EARLY pairing only. On
the current arms the trigger fires robustly on the largest frozen
subset - reached_any -0.1774 [-0.2251, -0.1315], reached_all -0.2849 -
and is recorded as fired. As before the metric is unresolvable at this
n: arm B's own replicate floor on reached_any is 0.2391, larger than
the gap.

The one effect that is real on the current arms is exposure:
chars_exposed -9,789 [-12727, -7075] against floors of 2,556 and 5,638.
The current arm B reads about a quarter as much document (3,344 vs
13,133 chars) for statistically identical answer quality, which is
exactly why reached_any falls while reached_by_read stays flat. Arm B
is also slower (+1,383 ms).

Unchanged across both pairings and now 2,941 tool calls: library_links
0 calls, follow walked the graph 0 times in 597 find calls, page
addressing 0, off-schema usage 0.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H9ToHYJVDxfeJcJwdzrP2H