Record slice B as proven with two unexercised branches

Neither will be manufactured: a second task hitting the same failure
exercises the eligibility transition, and a genuine repair exercises manual
intervention provenance.

Also records why the reasons check earned its place. An inference drawn
from aggregate numbers was wrong, and the pure explanation contradicted it
with counted facts.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CVbaKucEYBjMqVeUgJUsc1

DEBT-DESIGN.md

@@ -479,3 +479,42 @@ The first live consequence: the deploy restart of `79d2053` was not recorded,
 and `manual_intervention` stayed in the gap list afterwards. That is the
 correct result. Orchestra can record the evidence and this history contains
 none, which is an honest gap rather than synthetic evidence.
+
+## Slice B status, 2026-08-30
+
+```text
+worker observation durability         proven live
+incident open/close semantics         proven live
+high-water, no phantom recurrence     proven live
+task attribution                      proven live
+frozen historical provenance          proven live
+
+eligibility calculation               proven against real data
+eligibility transition                unexercised
+manual intervention recording         implemented
+manual intervention provenance        unexercised
+```
+
+Neither unexercised branch will be manufactured. A second task hitting the
+same failure exercises the first, and a genuine repair exercises the second.
+
+The proof that matters from the live run:
+
+```text
+recurrence 5, intensity 10, distinct tasks 1, interventions 0  ->  eligible=false
+```
+
+A noisy failure inside one task does not become system-level maintenance debt.
+The three counts stay separate on purpose: recurrence is how often the incident
+happened, intensity is how repetitive each incident became, and breadth is how
+many independent tasks paid for it. Operational debt requires breadth unless an
+operator had to intervene.
+
+### The reasons check is part of the design, not a formality
+
+The aggregate numbers moved in a way that looked like a promotion, and reading
+them that way was wrong: the eligible count rose because of an unrelated item.
+The pure eligibility explanation contradicted that inference with counted
+facts. That is the argument for the ledger resting on mechanically derived
+evidence rather than on anyone's reading of what looks recurring, including an
+agent's.