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.

pyproject.toml

@@ -60,9 +60,9 @@ Repository = "https://gitea.phasefinal.com/vh/ratatoskr"
 # Ratatoskr is built against Worldtree at this commit; the vendored
 # spec snapshot in docs/ reflects that SHA.
 [tool.ratatoskr.spec-pin]
-worldtree-spec-rev = "f1b59f8cd6fe41e497d0be9dad9d3110451f0d9a"
-worldtree-version = "v0.29.0"
-pinned-on = "2026-05-26"
+worldtree-spec-rev = "5810a26b38a5ea6630892f9a39756f57c5b7b41e"
+worldtree-version = "v1.0.0b2"
+pinned-on = "2026-06-30"
 
 # Bifrost lives on the auth-gated gitea PyPI index (not public PyPI).
 # uv reads the credential from UV_INDEX_GITEA_USERNAME / _PASSWORD or ~/.netrc.