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

workplans/INFD-WP-0001-founding-specs-and-approver-ui-ownership.md

@@ -237,7 +237,7 @@ are placeholders.
 
 ```task
 id: INFD-WP-0001-T06
-status: todo
+status: progress
 priority: high
 state_hub_task_id: "47cb3f7a-e349-5c81-a304-86275e058a85"
 ```
@@ -275,6 +275,30 @@ exercised in CI; the three published expected hashes reproduce byte-for-byte;
 the implemented-and-first-cut boundary rather than the aspiration, and no longer
 carries the T01 "nothing is implemented" banner.
 
+2026-09-09 — substantive half done; task stays `progress` because the `SCOPE.md`
+rewrite is gated on T02. Delivered:
+
+- `schemas/decision-memo.schema.json` plus both worked examples;
+  `informed_decision/canonicalize.py` as the governed canonicalizer, with the
+  ad-hoc `__main__` block replaced by `python -m informed_decision`;
+  fixtures under `tests/vectors/`. `history/` is untouched.
+- `tests/test_canonicalize.py` — 20 tests, all green. The three published
+  hashes reproduce byte for byte, and all four isolation properties are pinned.
+- `docs/specs/EvidenceModel.md`.
+- `pyproject.toml`, `Makefile` (`make test`, `make check`).
+
+Two things worth recording rather than burying:
+
+- Isolation properties 1, 2 and 4 are all *negative* — they assert the hash does
+  **not** change. A canonicalizer returning a constant would pass all three.
+  Property 3 plus per-field variants over `question`, `requested_act`,
+  `binding_level` and `packet` are what stop the suite being vacuous.
+- `test_governed_vectors_match_the_preserved_history_copy` asserts the governed
+  fixtures have not drifted from the founding copies, so quietly editing a
+  vector to make a failing test pass is itself a failure.
+
+Remaining for `done`: rewrite `SCOPE.md` after the T02 ruling.
+
 ## Publish the OIDC browser-client contract to key-cape
 
 ```task