Add SessionStop hook and session-events.tsv duration tracking

- session-audit.json: add SessionStop entry pointing to new end-of-session scripts
- report-hook-event-end.sh/.ps1: log payload to hook-events.log and write TSV row to session-events.tsv
- report-hook-event.sh/.ps1: also write SessionStart TSV row to session-events.tsv so start/end pairs are queryable for duration

resources/scripts/report-hook-event.ps1

@@ -6,6 +6,9 @@ New-Item -ItemType Directory -Path $StateDir -Force | Out-Null
 $Payload = [Console]::In.ReadToEnd()
 $Payload | Add-Content -LiteralPath (Join-Path $StateDir 'hook-events.log')
 
+# Append a TSV row to session-events.tsv for duration tracking.
+"$(Get-Date -AsUTC -Format o)`tSessionStart" | Add-Content -LiteralPath (Join-Path $StateDir 'session-events.tsv')
+
 $PortRegistryScript = Join-Path $PSScriptRoot 'update-port-registry.mjs'
 $NodeCommand = Get-Command node -ErrorAction SilentlyContinue
 if ($NodeCommand -and (Test-Path -LiteralPath $PortRegistryScript)) {