feat(provider): validate scope_filter against the v0.5 4-axis lattice

bifrost 0.7.0 (wire v0.5) makes agent_self canonical: the scope lattice is
now {end_user, group, tenant, agent_self}. Our store was MORE permissive than
bifrost's reference (no _validate_scope_filter), which silently 0-zeroed the
#295 cold recall instead of a loud 400. Now matched: search rejects an
out-of-lattice axis with InvalidFilter (-> memory.invalid_filter 400), agent_self
admitted. Purely additive — everything that validated before still validates.

Closes the parity gap our own foot-gun flag opened (bifrost-dev shipped the
lattice add #10 off it). Pin bumped bifrost>=0.6.1 -> >=0.7.0. Contract
search PRE-003 + lattice_axes test; 2 new store tests; full suite 429 green.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "ratatoskr"
-version = "0.17.4"
+version = "0.17.5"
 description = "Worldtree Conversation API debug TUI — multi-pane observability dashboard"
 readme = "README.md"
 requires-python = ">=3.12"
@@ -30,7 +30,7 @@ web = [
 # from the debug TUI. Recipe: bifrost/docs/implementing-a-consumer.md.
 provider = [
     "ratatoskr[web]",       # reuse the starlette + uvicorn ASGI stack
-    "bifrost>=0.6.1",       # consumer engines + library (0.6.0 yanked: circular import)
+    "bifrost>=0.7.0",       # consumer engines + library (0.7.0/wire-v0.5: agent_self canonical in the scope lattice; 0.6.0 yanked: circular import)
     "jsonschema>=4",        # bifrost runtime dep — envelope validation
     "sqlite-vec>=0.1.6",    # vector index for the memory plane (vec0 virtual table)
 ]