pin: re-pin to Worldtree's FROZEN v1 surface (OpenAPI 2.2.0 + SSE schema)

v1 coverage-audit remediation P-1: vendor the authoritative machine-
readable artifacts and pin them for drift-checking, advancing the spec
pin from v0.35.16 (f1b59f8) to v1.0.0b2 (5810a26).

- Vendor docs/conversation-api-openapi.json (OpenAPI 2.2.0, 40 path-
  groups) + docs/conversation-api-sse-events.schema.json (11 events).
- Pin all three Conversation-API artifacts in .corviduo-canonicals.toml:
  OpenAPI + SSE schema as strict drift gates (canonical_drift.py), the
  prose markdown as tolerate_drift reference. Drift check green (10/10).
- pyproject: worldtree-spec-rev -> 5810a26, worldtree-version -> v1.0.0b2
  (was stale at v0.29.0), pinned-on -> 2026-06-30.
- SPEC-PIN.md: current-pin table + history row + vendored-artifacts list.
- coverage-map.md: P-1 marked remediated; the map now audits a frozen,
  diffable target.

The prose markdown is byte-identical to v0.35.16 (last WT edit
2026-05-31); the b2 surface lives only in the OpenAPI. No client-
facing code change (the b2 409/503 + unified error envelope were
already consumed in v0.18.3/.4) -> pin-only, no version bump.

.corviduo-canonicals.toml

@@ -89,3 +89,37 @@ canonical_path = "scripts/contract_drift_check.py"
 consumer_path = "scripts/contract_drift_check.py"
 pinned_sha256_16 = "23271287ac488da4"
 pinned_at = "2026-05-17T05:30:00+00:00"
+
+# ---------------------------------------------------------------------------
+# Worldtree Conversation-API surface (vendored from ~/development/Worldtree).
+# The v1 wire is FROZEN (Worldtree #326 / v1-schema-freeze-manifest.md). The
+# machine-readable OpenAPI + SSE schema are the authoritative drift GATES; the
+# prose markdown is the human reference and is allowed to lag (tolerate_drift).
+# These are what ratatoskr's v1 coverage map (docs/coverage-map.md) audits
+# against. Pin target: Worldtree 5810a26 (v1.0.0b2).
+# ---------------------------------------------------------------------------
+
+[[pins]]
+id = "worldtree-conversation-api-openapi-v2"
+canonical_source = "Worldtree"
+canonical_path = "docs/conversation-api-openapi.json"
+consumer_path = "docs/conversation-api-openapi.json"
+pinned_sha256_16 = "dbdf4e24c8b06c92"
+pinned_at = "2026-06-30T22:25:56+00:00"
+
+[[pins]]
+id = "worldtree-conversation-api-sse-events-v1"
+canonical_source = "Worldtree"
+canonical_path = "docs/conversation-api-sse-events.schema.json"
+consumer_path = "docs/conversation-api-sse-events.schema.json"
+pinned_sha256_16 = "9deeebf404d72f9a"
+pinned_at = "2026-06-30T22:25:56+00:00"
+
+[[pins]]
+id = "worldtree-conversation-api-spec-v1"
+canonical_source = "Worldtree"
+canonical_path = "docs/conversation-api-spec.md"
+consumer_path = "docs/conversation-api-spec.md"
+pinned_sha256_16 = "2d111a3b8322b7d1"
+pinned_at = "2026-06-30T22:25:56+00:00"
+tolerate_drift = true  # prose reference; OpenAPI+SSE are the gates