Updated the scale operating layer PR with two concrete provider implementations:

• Added OpenSearchCandidateProvider for lexical candidate ids with workspace/ACL/document/source/time/property filters.
• Added QdrantCandidateProvider for vector candidate ids with payload filters and scored metadata.
• Kept both providers dependency-injected, so core imports do not require OpenSearch or Qdrant runtime packages.
• Updated PLAN-v0.31 near-term TODO to move the next focus to durable ingestion job/index health persistence and 100GB/1TB rehearsal.

Validation:

• uv run ruff check src/synaptic/indexing.py src/synaptic/init.py src/synaptic/init.pyi tests/test_indexing_contracts.py
• uv run pytest tests/test_indexing_contracts.py
• uv run pytest tests/test_evidence_search.py tests/test_graph.py tests/test_router.py tests/test_agent_tools.py tests/test_agent_search.py
• uv run pytest -> 1634 passed, 67 skipped
• GitHub CI lint/test passing on c6d9274

Added the durable operational-state foundation as well:

• MemoryBackend and SQLiteBackend now implement IngestionJobStore for stage/status/attempt/error/version/properties roundtrip.
• MemoryBackend and SQLiteBackend now implement IndexHealthBackend for provider lag reports, pending counts, failed jobs, p95 latency, and provider properties.
• PLAN-v0.31 now marks provider persistence as implemented and moves the next TODO to idempotent ingestion orchestration plus tombstone/replay flow.

Validation for this commit:

• uv run ruff check src/synaptic/backends/memory.py src/synaptic/backends/sqlite.py tests/test_indexing_contracts.py
• uv run pytest tests/test_indexing_contracts.py tests/test_backend_memory.py tests/test_backend_sqlite.py -> 82 passed
• uv run pytest tests/test_memory_operating_layer.py tests/test_memory_operating_poc.py tests/test_document_ingester.py tests/test_evidence_search.py tests/test_graph.py -> 161 passed
• GitHub CI lint/test passing on 2b1db24