docs(examples): add builder-adversary-min — minimal-prompt variant

Same topology/behaviour as builder-adversary (loop pair, phase machine,
claim()/review() handoff, machine-docs coordination, cold verification) but the
role + kickoff prompts are compressed to minimal tokens, keeping every
load-bearing rule. Config and plans are unchanged. The separate
agent-orchestrator-benchmark repo runs a head-to-head token comparison.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/builder-adversary-min/prompts/kickoff.md

@@ -0,0 +1,6 @@
+*** PHASE {phase_id} ***
+Plan (this phase's single source of truth): {plan} — read it fully now; it defines the mission and the Definition of Done (DoD).
+Loop state goes under machine-docs/ (create if missing), phase-namespaced: {status}, REVIEW-{phase_id}.md, JOURNAL-{phase_id}.md, BACKLOG-{phase_id}.md. Never at the repo root.
+Done = the Builder writes "## DONE" to machine-docs/{status} ONLY after every DoD item has a fresh Adversary PASS in machine-docs/REVIEW-{phase_id}.md.
+
+=== role ===