Persist a directional investment thesis (bull / bear / neutral) on a ticker. The thesis becomes part of the caller's private research diary; pair with `list_theses` + `score_thesis_outcome` to track conviction-vs-outcome over time. Pass `idempotency_key` for at-most-once semantics from a retrying agent.
**Use this AFTER** the agent has finished its analysis, not before — the thesis records the conclusion, not the question. Pair with `source_report_id` to link the thesis back to a published report so the buyer's thesis-tracking carries provenance.
Tier: all paid + free tiers (sample tier rejected — sample is guest access with no customerId binding). Per-tier cap on # of stored theses: sp500=100, pro=500, full=10,000.
Connector