fd-knowledge-graph: summarize retrieval evidence routes in CLI output

[ronsse]

Context

• retrieve query-history --json exposes full graph-safe context, including evidence_routes, but non-JSON output previously printed the context dict directly.
• Operators need a bounded readable summary to inspect route decisions during POC validation without scrolling through every evidence property.

Stacked implementation

• fd-knowledge-graph branch stack/retrieval-route-cli, stacked on PR Planes Phase 4 \xe2\x80\x94 document_ids link on the GraphStore contract (Kuzu parts deferred) #6 / stack/documentation-evidence-roles.
• Non-JSON retrieve query-history now prints Anchors, Evidence Routes, Evidence Counts, and Warnings.
• JSON mode remains unchanged and returns {status, context}.

Safety

• Human output does not expand evidence properties or raw context payloads.
• It emits route ids, primary evidence, ordered evidence sources, counts, and warnings only.

Verification

• ruff check . passed.
• pytest -q passed: 196 tests, 1 existing requests dependency warning.
• git diff --check passed.