feat(vector): add direct pgvector adapter

.superpowers/sdd/pgvector-task-1-report.md

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+# Local pgvector Task 1 report
+
+## Status
+
+Implemented the direct `PgVectorStore` behind the transport-neutral `VectorStore` port.
+The adapter uses separate optional reader and writer database configurations, derives
+capabilities from configured authority, validates strict positive search limits, filters kinds
+in SQL before limiting, and merges multi-collection results by cosine similarity.
+
+All collection identifiers are selected from the fixed `schema_records`, `evidence`, and
+`memory` allowlist and composed with `psycopg2.sql.Identifier`. Values, vectors, kinds, hashes,
+and limits remain bound parameters. Collection/kind mismatches fail with `VectorStoreError`.
+
+Upserts preserve the canonical metadata shape, use `record_key` conflict semantics, update the
+transport hash and embedding, and leave semantic metadata fields intact. Health probes reader
+and writer independently and reports observed `vector(N)` dimensions against the configured
+embedding dimension.
+
+## Configuration and factory
+
+`pgvector_direct` now accepts explicit optional `reader` and `writer` `DatabaseConfig` entries.
+The former `connection` entry remains supported as a deprecated read-only compatibility path.
+`build_vector_store(..., require_write=True)` accepts writer-only direct configurations and
+fails early when no explicit writer is present.
+
+The transitional `build_vector_loader` bulk-sync path remains in place. It uses an explicit
+direct writer when present, or the legacy `connection`; it deliberately does not treat a new
+reader-only credential as writable. No production schema migration was added.
+
+## TDD and verification
+
+- RED: the new tests initially failed at collection because `PgVectorStore` did not exist.
+- Docker L0 pgvector tests: `11 passed`.
+- Direct + HTTP parity/factory/config focus: `51 passed`.
+- Full harness: `461 passed, 5 deselected`.
+- Changed-file Ruff lint: clean.
+- Changed-file Ruff format check: clean.
+- `git diff --check`: clean.
+
+The repository-wide `ruff check .` still reports 34 pre-existing test-file findings outside
+Task 1; none are in changed files. The full pytest suite emits 17 existing legacy-config
+deprecation warnings.
+
+## Scope and concerns
+
+- Test fixtures create only the three existing vector tables needed to exercise the adapter;
+  migration/versioning remains Task 2.
+- The legacy single `connection` form stays read-only through the public port, matching its
+  previous adapter behavior, while remaining available to the explicitly documented bulk-loader
+  transition.