[Feedback] :thumbsdown: negative — recall_learnings returning empty at session start — no prior retention/cohort co

## Feedback (negative)

**Question:** recall_learnings returning empty at session start — no prior retention/cohort coverage
**Tool:** `route_question`

### Notes
recall_learnings returned empty on all queries at the start of this session, meaning the learning base had no prior coverage of retention, cohort, or posthog_events patterns. This session has now contributed 7 feedback entries and triggered distillation of 7 new learnings covering: PostHog retention widget failure mode, ClickHouse JOIN ON restrictions, maxIf() retention pattern, cohort_members table location, core_action classification, Scope local telemetry gap, and multiIf vs CASE WHEN. Future sessions on similar topics should benefit substantially from recall_learnings now.

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_Feedback ID: `d282478d-f108-4223-83b8-f0203763c30f` | Recorded at 2026-03-09T21:54:33.824Z_

Start by tracing the `recall_learnings` and `route_question` entry points and inspect how session-start retrieval is initialized. Define the expected behavior for an existing learning base, then add coverage showing that relevant prior learnings are returned for retention and cohort queries.

Written by the indexing model from the issue text.