Prevent duplicate desktop model sessions and record calibration evidence

docs/RELEVANCE-CALIBRATION.md

@@ -14,8 +14,9 @@ an exploratory topic query, so these absence labels require concrete artifacts.
 The source inventory and blinded review have been completed. Independent AI
 review agreed with all expected file sets; the final labels are frozen in
 `fixture.json` with hashes and a UTC timestamp in `fixture.lock.json`.
-No retrieval run, threshold selection or ranking change has occurred. Agent
-agreement will not be described as human review.
+The calibration-only baseline has run with genuine Google CPU inference.
+No threshold selection or ranking change has occurred. Agent agreement will
+not be described as human review.
 
 The first independent agent review detected Windows-1252 mojibake in the
 authored German requests and ambiguity in the wildcard-comparator request.
@@ -46,3 +47,32 @@ why instead of altering this diagnostic silently.
 
 This small corpus does not close independent human relevance, media abstention,
 music discrimination, speech localisation or production-scale quality gates.
+
+## Recorded CPU baseline, 2026-10-13
+
+The shared-engine runner completed all 24 calibration requests plus six code
+intent requests repeated under Code scope. Held-out requests were not evaluated.
+All 14 frozen sources remained available as distractors.
+
+| Scope | Positive requests | Lexical top-1 | Semantic / hybrid top-1 | Absent requests returning semantic / hybrid neighbours |
+| --- | --- | --- | --- | --- |
+| All files | 16 | 1/16 | 16/16 | 8/8 |
+| Additional Code scope requests | 4 | 0/4 | 4/4 | 2/2 |
+
+The additional code rows repeat intents; they are not independent observations.
+Lexical search returned no results for the absent requests. Semantic similarity
+still retrieves related neighbours when the requested source is absent. This
+baseline therefore supports useful positive retrieval, but does not establish
+reliable abstention or justify a cutoff chosen without further calibration.
+
+Ignored raw evidence: `.searchi/qa/calibration-v2-baseline.json`, SHA-256
+`56f42c523527dd748918bb8f17be6bd7818158227e692fccaf387d915f9d0a94`.
+The report records completion, calibration split and `held_out_evaluated: false`.
+Frozen fixture SHA-256:
+`000047fd17accd315b6138093bbdc9f353cd877b4bf1958fbe336e4a6b10cd2e`.
+
+This ordered debug diagnostic used one CPU thread and the normal worker
+`c01cb3ec13cfca722ee768e8350e1399a8b9a4d14a24a35adc3473a5cfc82a73`.
+Lexical indexing took 19.9823 ms, semantic indexing 74,545.518 ms and retained
+query-session startup 7,433.3914 ms. These are diagnostic setup measurements,
+not native first-search latency or warm production p95.