docs(echidnabot/agentic): record BoJ-only-MCP exception carve-out

Adds `[exceptions.boj-only-mcp]` to echidnabot's AGENTIC.a2ml with:
- reason: direct-callable for proof-op agents (Sonnet executors,
  Haiku scouts need sync call-and-response against the panic-attack
  CLI wrapper; BoJ's async message-bus does not yet provide it)
- scope: this repo only
- sunset condition: when BoJ cartridge supports the double-loop
  feedback protocol (bidirectional calibration per the Bullshit
  Field design)
- decision date: 2026-04-24, Jonathan D.A. Jewell

This keeps the estate-wide "BoJ-only MCP" rule intact while
documenting echidnabot's time-bound carve-out in-tree so future
agents can read the justification instead of re-litigating it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

echidnabot/.machine_readable/6a2/AGENTIC.a2ml

@@ -32,3 +32,18 @@ release-claim-requires-hard-pass = true
 # on-enter: Read 0-AI-MANIFEST.a2ml, then STATE.a2ml
 # on-exit: Update STATE.a2ml with session outcomes
 # on-commit: Run just validate-rsr
+
+[exceptions]
+# Carve-outs from estate-wide standing rules, justified and time-bound.
+# Each exception MUST declare: rule, reason, scope, sunset-condition, decision-date.
+
+[exceptions.boj-only-mcp]
+rule            = "BoJ-only MCP (all MCP routes through BoJ; no standalone MCPs)"
+status          = "approved"
+decision-date   = "2026-04-24"
+decided-by      = "Jonathan D.A. Jewell <j.d.a.jewell@open.ac.uk>"
+reason          = "direct-callable for proof-op agents — echidnabot wraps the panic-attack CLI and is invoked synchronously by proof-operation agents (Sonnet executors, Haiku scouts) that need call-and-response semantics the BoJ cartridge's async message-bus does not currently provide."
+scope           = "this repo only (echidnabot)"
+sunset-condition = "when the BoJ cartridge supports the double-loop feedback protocol (synchronous call-and-response with bidirectional calibration signals, matching the Bullshit Field design)."
+sunset-action   = "migrate echidnabot invocations onto the BoJ double-loop transport, verify parity against the current direct-callable surface, then delete this [exceptions.boj-only-mcp] block."
+upstream-tracking = "BoJ double-loop protocol is tracked in boj-server's STATE.a2ml; review quarterly."