feat(profiling): P5-① e2e hybrid recall@10 (LOC-70)

[dev07060]

Summary

• Adds Dart-side f32 ground-truth recall helpers and read-only SQLite corpus loading for the example profiler.
• Adds an iPhone profile recall harness comparing frozen-query GT against vector-only and shipped hybrid search.
• Records the P5-① result in docs/perf/ondevice-query-profiler/PR-P5-1.html and updates the profiler README status.

Result

• iPhone profile run passed with --no-dds.
• mean recall_vectoronly@10 = 1.00
• mean recall_hybrid@10 = 0.08
• Verdict: vector-only quality gate passes; hybrid value is a BM25/RRF reorder diagnostic against pure-vector GT, not an HNSW failure.

Verification

• flutter test test/profiling/recall_math_test.dart test/profiling/recall_db_test.dart test/profiling/recall_report_test.dart
• flutter test -d macos integration_test/query_recall_measure_test.dart
• flutter drive --driver=test_driver/integration_test.dart --target=integration_test/query_recall_measure_test.dart --profile --no-keep-app-running --no-dds --device-timeout=60 -d 00008110-001524992E38801E

[linear-code]

LOC-70