semantic-search: retrieve from the Query Planner directly (replace the GraphQL hop)

[bjagg]

Part of the ADR-0003 epic #1105. Plan: docs/operations/proposals/advisor-qp-direct-retrieval.md (PR #1104). Decision: ADR-0003.

Goal: The core ADR-0003 rewire — semantic-search retrieves from the QP directly instead of via GraphQL.

Scope:

• Inject LIF_QUERY_PLANNER_URL into semantic-search (CloudMap target exists: query-planner-${Org}.lif.${Env}.aws:8002; semantic-search has no QP env today, cloudformation/lif-semantic-search-taskdef-includes.yml).
• Replace the graphql_client call (semantic_search_service/core.py:424-426) with a QP async client using brick D and the QP key from C.
• Keep GraphQL wired and demoable as its own peer consumer of the QP.

Size: L · Depends on: B, C, D