Sprint 249 Plan: Raw Candidate No-Uplift Guardrail

Goal

Prevent false confidence from raw candidate search runs that try variants but produce no measurable uplift.

Step 2290: Add baseline vs best raw candidate comparison telemetry.
Step 2291: Emit raw candidate search artifact for every enabled run.
Step 2292: Add optional hard-fail guard when no failing-profile uplift is achieved.
Step 2293: Validate expected pass/fail behavior for guardrail mode.
Step 2294: Add Sprint249IntegrationSummary.h and execution tracker.