Build the T08 domain core with the engine behind a seam

approval-engine APPROVAL-WP-0002-T01 is still progress and its namespace has no
pods, so the live end-to-end proof cannot run. Built everything that does not
depend on it, with the engine behind a Protocol plus a fake carrying its real
refusal semantics, so its arrival is a wiring change rather than a build.

- memo.py: the Decision Memo, versions, binding document. Principal, Scope,
  Awareness and Hat are dataclasses rather than dicts because the canonicalizer
  requires a shape and a missing key should fail at construction rather than
  deep inside hashing — which is exactly how it failed twice while building
  this. Field names follow the governed canonicalizer (item_id, severity,
  locator): the published vectors are the contract, so the object was aligned to
  them rather than the reverse.
- presentation.py: the sole writer of view_hash. One writer, one canonicalizer,
  one place to audit. Acknowledgment is an explicit method call and nothing
  infers it from scroll, dwell or focus.
- disposition.py: verbs and guards G_NOAGENT, G_STEP, G_PRES, G_ACK, G_REASONS,
  G_SEALED. accept is ABSENT from weak steps rather than present-and-disabled,
  because a greyed-out accept still teaches the wrong model. Only accept reaches
  the engine; a memo return is not represented there at all.
- provenance.py: claim routes per A-16. assert_human_control_dischargeable
  refuses a registration-supplied human, so PR-11's limitation fires at the
  point of use instead of sitting in a document.
- evidence.py: local outbox, commitment-only records carrying the
  GH-DEC-2026-014 §4 existence assertion, per-class reconciliation counts, and a
  custody-locator guard that rejects credentialed URLs (PR-12).
- approval_client.py: 409 duplicate_approver is success, 409 conflict terminal,
  503 fail-closed, approval:consume refused before a token is requested.

87 tests pass, including every negative case in the Use Case Catalog and that a
fail-closed outcome is recorded as a stance application with no verb field —
never as a decline, because the human did not make one.

T08 stays progress: the live proof is the remainder.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V3W1dQG7GFFM9d94jFx7iR

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1565372@bnt-lap001
Assistant-Session: 16bb2f25-b34c-49ef-8e94-5fec3567a568

informed_decision/presentation.py

@@ -0,0 +1,92 @@
+"""Presentation records — the sole writer of ``view_hash``.
+
+One writer, one canonicalizer, one place to audit. A second path that computes
+a hash is a defect, not an optimisation (`ArchitectureBlueprint` §3).
+
+A presentation is a record of an event that happened. It is append-only:
+editing one is falsifying evidence.
+"""
+
+from __future__ import annotations
+
+import uuid
+from dataclasses import dataclass, field
+from datetime import datetime, timezone
+from enum import Enum
+
+from .canonicalize import awareness_hash, view_hash
+from .memo import Awareness, Memo
+from .provenance import Claim
+
+
+class Phase(str, Enum):
+    PRE_BIND = "pre_bind"
+    BIND = "bind"
+    POST_BIND = "post_bind"
+
+
+def _now() -> str:
+    return datetime.now(timezone.utc).isoformat(timespec="seconds").replace("+00:00", "Z")
+
+
+@dataclass(frozen=True)
+class Presentation:
+    id: str
+    memo_id: str
+    memo_version: int
+    principal_sub: str
+    locale: str
+    ui_release: str
+    rendered_at: str
+    view_hash: str
+    awareness_hash: str
+    phase: Phase
+    #: Co-reference to the act (GH-DEC-2026-012 R3). The identifier only.
+    approval_id: str | None = None
+    #: Claims stored WITH their route, never as bare strings (PR-09, PR-11).
+    tenant: Claim | None = None
+    principal_type: Claim | None = None
+    acked_highlight_ids: frozenset[str] = field(default_factory=frozenset)
+
+    def with_ack(self, highlight_id: str) -> "Presentation":
+        """Acknowledgment is an explicit act.
+
+        Never inferred from scroll position, dwell time, focus or viewport
+        intersection (PR-21). Only this method records one, and only a
+        deliberate control activation calls it.
+        """
+        from dataclasses import replace
+
+        return replace(self, acked_highlight_ids=self.acked_highlight_ids | {highlight_id})
+
+
+def render(
+    memo: Memo,
+    *,
+    principal_sub: str,
+    tenant: Claim | None = None,
+    principal_type: Claim | None = None,
+    awareness: Awareness | None = None,
+    phase: Phase = Phase.PRE_BIND,
+) -> Presentation:
+    """Render a memo, producing exactly one presentation record.
+
+    This is the only function in the package that computes ``view_hash``.
+    """
+    binding_doc = memo.binding_document()
+    awareness_doc = memo.awareness_document(awareness)
+    return Presentation(
+        id=f"pres-{uuid.uuid4()}",
+        memo_id=memo.id,
+        memo_version=memo.version,
+        principal_sub=principal_sub,
+        locale=memo.locale,
+        ui_release=memo.ui_release,
+        rendered_at=_now(),
+        view_hash=view_hash(binding_doc)["hex"],
+        awareness_hash=awareness_hash(awareness_doc)["hex"],
+        phase=phase,
+        approval_id=memo.approval_id,
+        tenant=tenant,
+        principal_type=principal_type,
+    )