feat(provider): memory plane — SQLite+sqlite-vec store + dev shell

The second plane of ratatoskr's Tier-3 Bifrost consumer: a durable memory
store Worldtree writes agent memory chunks into (upsert_many) and recalls
by vector similarity (search), with point reads + deletes. Implements
bifrost's own MemoryDataStore Protocol; conformance is #195 parity vs
InMemoryMemoryStore through the real dispatch_memory_call.

Store (memory_store.py): open_memory_store, describe_store, upsert_many
(replay/conflict idempotency, optimistic locking, injection rule, atomic
batch), search (cosine over sqlite-vec vec0, scope isolation INV-005,
over-fetch-then-filter so top_k counts in-scope), get/get_many,
delete_many, build_memory_provider_app. Dev shell (serve_memory.py):
ratatoskr-memory-provider entrypoint, port 8391.

TDD + heid-code-review (panel Groa/Hulda/Regin, zero true drift). Adopted
fixups: scope_filter dict guard, top_k<=0 -> [], stronger scope-isolation
+ delete-hit-search + handshake-POST tests. Partial-map optimistic-lock
semantics pinned against the reference via a new expected_revisions
parity test.

26 memory + 4 serve tests; #195 parity (upsert/search/expected_revisions)
green; ruff clean. Deps: +sqlite-vec.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "ratatoskr"
-version = "0.17.2"
+version = "0.17.3"
 description = "Worldtree Conversation API debug TUI — multi-pane observability dashboard"
 readme = "README.md"
 requires-python = ">=3.12"
@@ -32,6 +32,7 @@ provider = [
     "ratatoskr[web]",       # reuse the starlette + uvicorn ASGI stack
     "bifrost>=0.6.1",       # consumer engines + library (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)
 ]
 dev = [
     "pytest>=8",
@@ -45,9 +46,10 @@ dev = [
 ]
 
 [project.scripts]
-ratatoskr          = "ratatoskr.cli:main"
-ratatoskr-web      = "ratatoskr.web.entrypoint:main"
-ratatoskr-provider = "ratatoskr.provider.serve:main"
+ratatoskr                 = "ratatoskr.cli:main"
+ratatoskr-web             = "ratatoskr.web.entrypoint:main"
+ratatoskr-provider        = "ratatoskr.provider.serve:main"
+ratatoskr-memory-provider = "ratatoskr.provider.serve_memory:main"
 
 [project.urls]
 Repository = "https://gitea.phasefinal.com/vh/ratatoskr"