agent discipline: land on the default branch, add section 12

The doc has only ever lived on `agent-discipline-preload`, so no agent has
ever loaded it -- a preload on a non-default branch never runs.

Section 12, A VERDICT IS THREE-VALUED: MEASURED_PASS / MEASURED_FAIL /
NOT_MEASURED with a mandatory reason. A clock may measure, it may never
judge. Every verdict carries its vantage. And the mirror failure, a step
that cannot fail -- if the thing under test were completely broken right
now, would this step turn red?

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

AGENT-PRELOAD.md

@@ -0,0 +1,12 @@
+# Agent preload
+
+**Read [`AGENT-DISCIPLINE.md`](AGENT-DISCIPLINE.md) first, before anything else
+in this repository.**
+
+It is the operating discipline for every agent and sub-agent: run the check
+before you assert a limit, do not abandon a computed result under pressure,
+state your encoding, tag every claim MEASURED / NAMED / CONJECTURE, keep
+retractions beside the claims they correct, and emit three-valued verdicts --
+MEASURED_PASS / MEASURED_FAIL / NOT_MEASURED with a reason (see section 12).
+
+Operator and author of the laws: Jesse Daniel Brown (OP-JESSE).