pin: bump Worldtree spec to f1b59f8 (v0.35.16) — cold recall closes end-to-end

Worldtree shipped its half of the union-recall fix: #297 (client-side
per-scope-value union recall) + #298/#299 (adopt the bifrost v0.6
scope_any/scope_all wire, v0.35.16). It now emits scope_any on the recall
path, pairing with our v0.17.6 provider — cold cross-session recall is
closed end-to-end (pending a live re-smoke against a v0.35.16 instance).

Re-vendored conversation-api-spec.md + conversation_api.contract.md;
285-commit catch-up (v0.29.0 -> v0.35.16). Diff-reviewed: no client-facing
breaking changes for our consumer.

- #211 agent-slug rename (saga->echo, actor->mask) — slugs only, we pass --agent
- #245 end_user_id persistence + memory-scope resolver (additive)
- #187/#188/#219 Tier-3 define/PATCH policy (additive); error codes stable
- bifrost binding field + ephemeral_does_not_accept_bifrost 422 now documented (#17 surface)
- docs: SPEC-PIN.md pin table + history; bifrost-self-test recall status; persistent-memory

No package version bump (docs/pin-only, no ratatoskr code change).

pyproject.toml

@@ -59,7 +59,7 @@ 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 = "562001af28d752c3a60d449c7ddd09f44fa9dc9a"
+worldtree-spec-rev = "f1b59f8cd6fe41e497d0be9dad9d3110451f0d9a"
 worldtree-version = "v0.29.0"
 pinned-on = "2026-05-26"