# Time-to-Evidence (TTE) metric instrumentation and percentile export

## Module
Telemetry

## Status
IMPLEMENTED

## Description
TTE metrics capture and percentile export are implemented in the Telemetry.Core library with DI registration support.

## Implementation Details
- **TimeToEvidenceMetrics**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/TimeToEvidenceMetrics.cs` -- meter `StellaOps.TimeToEvidence` with:
  - `tte_phase_latency_seconds` -- histogram for per-phase latency
  - `tte_scan_duration_seconds` -- histogram for total scan duration
  - `tte_phase_completed_total` -- counter for completed phases
  - `tte_phase_failed_total` -- counter for failed phases
  - `tte_slo_breach_total` -- counter for SLO breaches
  - `tte_evidence_attached_total` -- counter for evidence attachments
  - `tte_decision_made_total` -- counter for decisions made
- **TtePercentileExporter**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/TtePercentileExporter.cs` -- custom OTEL exporter for p50/p90/p99 percentile export
- **TimeToFirstSignalMetrics**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/TimeToFirstSignalMetrics.cs` -- TTFS metrics for first signal detection
- **TimeToFirstSignalOptions**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/TimeToFirstSignalOptions.cs` -- TTFS configuration
- **TtfsIngestionService**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/Triage/TtfsIngestionService.cs` -- ingests TTFS events for metrics
- **TtfsEvent**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/Triage/TtfsEvent.cs` -- TTFS event model
- **ScanCompletionMetricsIntegration**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/ScanCompletionMetricsIntegration.cs` -- integrates scan completion into TTE pipeline
- **UnknownsBurndownMetrics**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core/UnknownsBurndownMetrics.cs` -- tracks unknowns burndown rate
- **Tests**: `src/Telemetry/StellaOps.Telemetry.Core/StellaOps.Telemetry.Core.Tests/TimeToFirstSignalMetricsTests.cs`, `TtfsIngestionServiceTests.cs`
- **Source**: Feature matrix scan

## E2E Test Plan
- [ ] Verify TTE phase latency histogram records per-phase timing accurately
- [ ] Test percentile exporter produces p50/p90/p99 values for TTE metrics
- [ ] Verify SLO breach counter fires when phase latency exceeds threshold
- [ ] Test TTFS metrics capture time from CVE disclosure to first signal detection
- [ ] Verify scan completion integration records evidence attachment timing
- [ ] Test unknowns burndown metrics track reduction rate over time