feat: add spring ai retrieval sidecar

openspec/specs/rag-knowledge-retrieval/spec.md

@@ -82,3 +82,27 @@ The system SHALL persist compact evidence block summaries in `tool_invocation.re
 #### Scenario: Full content is not duplicated into retrieval details
 - **WHEN** evidence block summaries are persisted
 - **THEN** full evidence content SHALL be omitted or truncated so the trace record remains compact
+
+### Requirement: Knowledge retrieval SHALL support a disabled-by-default Spring AI sidecar
+The retrieval system SHALL allow a Spring AI VectorStore retrieval path to be wired as a sidecar without changing the default `lookup_knowledge` runtime path.
+
+#### Scenario: Sidecar disabled by default
+- **WHEN** the application starts without explicit sidecar enablement
+- **THEN** `lookup_knowledge` SHALL continue using the existing retrieval path
+- **AND** Chat and AIOps runtime behavior SHALL not depend on the sidecar
+
+#### Scenario: Sidecar failure does not break main retrieval
+- **WHEN** the Spring AI sidecar is enabled but cannot initialize or query successfully
+- **THEN** the existing retrieval path SHALL remain usable
+- **AND** the failure SHALL be reported as sidecar status rather than as a main retrieval failure
+
+### Requirement: Knowledge retrieval SHALL normalize sidecar results for comparison
+The sidecar retrieval path SHALL expose results in a comparable structure aligned with the current retrieval result shape.
+
+#### Scenario: Comparable result metadata
+- **WHEN** sidecar retrieval returns candidates
+- **THEN** each comparable result SHALL include source or doc id, title when available, breadcrumb when available, category when available, rank, content preview, and the sidecar score label/value
+
+#### Scenario: Score semantics are explicit
+- **WHEN** current retrieval and sidecar retrieval scores are compared
+- **THEN** the report SHALL label score semantics by path instead of assuming direct numeric equivalence