feat(ai): add Valkey vector store backend - #1544

- Exercises the provider against a real valkey-search server via
  valkey/valkey-bundle:9.1.2, pinned for reproducibility
- Covers KNN distance ordering, field and metadata round trip, upsert
  replacement, maxResults beyond the default limit of 10, namespace
  isolation under a shared index name, concurrent first writes, and index
  reuse by a second instance
- Host and mapped port are read from the container, so the test runs
  unchanged alongside an existing Valkey on the default port
- Declares org.testcontainers:testcontainers explicitly rather than relying
  on it transitively

Signed-off-by: Anna Tao <annatao2004@gmail.com>

- Add a Valkey section to VECTORDB_CONFIGURATION.md: configuration example,
  all 11 properties with defaults and validation constraints, key and index
  naming scheme, and troubleshooting entries
- Record that score is a raw cosine distance where lower is closer, and warn
  that MongoDB and Pinecone return the opposite convention
- State the standalone-only scope and the valkey-search module requirement
- Source the password from the environment in the example rather than inline
- List Valkey alongside the existing providers across the AI and concept docs,
  updating the vector database count from three to four

Signed-off-by: Anna Tao <annatao2004@gmail.com>

- Fail startup instead of silently dropping a vector DB instance whose
  configuration or construction throws (VectorDBProvider,
  VectorDBInstanceConfig)
- Anchor Valkey already-exists/unknown-command error classification to
  the verified GLIDE message shape instead of free-floating substring
  matches
- Validate document ids against the same allowlist used for
  indexName/namespace before key construction
- Set a GLIDE clientName for CLIENT LIST observability on shared
  Valkey servers

Signed-off-by: Anna Tao <annatao2004@gmail.com>

Test comments referenced internal QA-review finding IDs (M0/M1/N1/L1)
that only make sense with the review doc, which isn't part of this
PR. Rewritten to describe the behavior each test verifies on its own.

Signed-off-by: Anna Tao <annatao2004@gmail.com>

- Close already-created vector DB instances before throwing the
  startup aggregate exception, instead of leaking their connections
- Only fail startup for configuration errors; log and skip runtime/
  connectivity failures, matching how Postgres/Mongo/Pinecone already
  behave (Valkey is the only backend that connects eagerly)
- Clear VectorDBProvider's map after dispose() so a lookup after
  shutdown returns null instead of an already-closed instance
- Preserve the stack trace in the dispose() close-failure log
- Reject a blank/null Valkey instance name with a clear error instead
  of an opaque NullPointerException

Signed-off-by: Anna Tao <annatao2004@gmail.com>

Catching bare RuntimeException to tolerate a transient Valkey connection
failure at startup also silently swallowed genuine bugs (NPE,
ClassCastException) from any backend. Add ValkeyConnectionException as a
distinct type thrown only for GLIDE connection-establishment failures,
and narrow VectorDBInstanceConfig's skip-path catch to that type so any
other RuntimeException still fails startup loudly.

Signed-off-by: Anna Tao <annatao2004@gmail.com>

- GLIDE client creation (TCP+TLS+AUTH+SELECT) routinely takes longer
  than a single command, especially cross-AZ. Give it its own timeout
  (creationTimeoutMs = max(requestTimeoutMs * 3, 5000ms)) instead of
  reusing the per-command requestTimeoutMs, which could spuriously
  trip and cause a healthy instance to be skipped at startup.
- Close a narrow race in VectorDBProvider: a concurrent get() call
  could return an instance that dispose() was in the middle of
  closing. Set a disposed flag at the start of dispose(), checked in
  get(), so lookups start returning null immediately rather than
  racing the close loop.

Signed-off-by: Anna Tao <annatao2004@gmail.com>

Move FT.CREATE network I/O outside ConcurrentHashMap mapping functions.\n\nUse deadline-based polling with diagnostic timeout failures in Valkey round-trip tests.

Signed-off-by: Anna Tao <annatao2004@gmail.com>

- Support GLIDE alternating key-value arrays
- Validate dimensions from existing vector indexes
- Add regression coverage for the runtime response shape

Signed-off-by: Anna Tao <annatao2004@gmail.com>

Signed-off-by: Anna Tao <annatao2004@gmail.com>

Signed-off-by: Anna Tao <annatao2004@gmail.com>

Signed-off-by: Anna Tao <annatao2004@gmail.com>