Promote schema and canonicalizer out of history; add EvidenceModel (T06)

Verified the three published hashes reproduce byte for byte before promoting
anything, then moved the schema, canonicalizer and vectors into governed assets.
history/20260909-initial-exploration/ is untouched and stays the provenance
record.

- schemas/, informed_decision/, tests/vectors/ populated; the reference
  canonicalizer's ad-hoc __main__ block replaced by a real
  `python -m informed_decision` entry point.
- tests/test_canonicalize.py — 20 tests, all green. Published vectors, all four
  isolation properties, canonical-form round-trip, key sorting, and a provenance
  test asserting the governed fixtures have not drifted from history/.
- docs/specs/EvidenceModel.md — the two hashes, the split and why it exists, the
  four isolation properties, the presentation record, the bundle, and the
  relationship to audit-core.
- pyproject.toml, Makefile.

One test of mine was wrong on first run: it scanned for ", " to assert no
insignificant whitespace, which fires on prose inside a brief. Replaced with a
canonical round-trip comparison, which is the property actually meant. The
canonicalizer was correct.

EvidenceModel leads with what the model does NOT claim — no proof of
comprehension, no proof of reading (deliberately, since the alternative is
surveillance), no survival of a compromised surface, and audit-core's inherited
bound that a hash chain cannot prove a record was never sent.

T06 stays progress: the SCOPE.md rewrite is gated on the T02 ruling.

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

tests/vectors/login-awareness.json

@@ -0,0 +1,63 @@
+{
+  "memo_id": "01K4LOGIN00000000000000001",
+  "memo_version": 1,
+  "locale": "en",
+  "ui_release": "informed-decision@0.4.0",
+  "proposed_hat": {
+    "id": "hat:finance-controller",
+    "label": "Finance Controller",
+    "kind": "access_profile",
+    "elevates": false,
+    "permissions_preview": ["invoice.read", "invoice.export"],
+    "scope_id": "tenant:acme"
+  },
+  "proposed_hat_source": "last_used",
+  "available_hats": [
+    {
+      "id": "hat:finance-controller",
+      "label": "Finance Controller",
+      "kind": "access_profile",
+      "elevates": false,
+      "permissions_preview": ["invoice.read", "invoice.export"],
+      "scope_id": "tenant:acme"
+    },
+    {
+      "id": "hat:auditor-readonly",
+      "label": "Auditor (read-only)",
+      "kind": "perspective",
+      "elevates": false,
+      "permissions_preview": ["invoice.read"],
+      "scope_id": "tenant:acme"
+    },
+    {
+      "id": "hat:payroll-admin",
+      "label": "Payroll Admin",
+      "kind": "role",
+      "elevates": true,
+      "permissions_preview": ["payroll.run", "employee.export-all"],
+      "scope_id": "tenant:acme"
+    }
+  ],
+  "available_scopes": [
+    {
+      "kind": "tenant",
+      "id": "tenant:acme",
+      "label": "ACME Corp",
+      "environment": "prod",
+      "requires_new_bind": true
+    },
+    {
+      "kind": "tenant",
+      "id": "tenant:beta",
+      "label": "Beta GmbH",
+      "environment": "prod",
+      "requires_new_bind": true
+    }
+  ],
+  "last_session": {
+    "ended_at": "2026-09-08T16:12:00Z",
+    "hat_id": "hat:finance-controller",
+    "scope_id": "tenant:acme"
+  },
+  "situation_note": "Last session Tuesday 18:12 CEST as Finance Controller in ACME. Payroll Admin is an elevating hat and needs its own bind."
+}